muddy shores near low-water mark. The young, from several inches to
a foot long, are common. When full-grown some attain the length of
twelve or thirteen feet, and are an inch in breadth and quite flat
when extended, but can contract to two or three feet in length,
and are then nearly cylindrical. This worm, although so soft,
penetrates the sand with great rapidity. Its head changes shape
constantly and assists the proboscis when burrowing. It is also
able to swim. Its color is yellowish or flesh-color, with whitish
edges and a central band.
^M. rosea.^ The largest specimens are six to eight inches long and
one quarter of an inch broad; lives in burrows on sandy beaches;
color red or pink; often covered with sand, which adheres to the
mucus which the worm secretes. [pg170]
GENUS ^Cerebratulus^
^C. angulatus.^ Olive-green, with light dorsal stripe.
GENUS ^Cosmocephala^
^C. ochracea.^ Two to three inches long when extended; gray or
yellowish-white, and mottled by the internal organs showing through
the translucent body; line of lighter color down the back; anterior
end often orange-colored. It is common near low-water mark under
stones and in the dead tubes of /Serpula/.
GENUS ^Polina^
^P. glutinosa.^ One to two inches long; color orange or light
yellow, with a faint line of deeper color down the center of the
dorsal surface; very slimy; eyes numerous, in oblique lines on the
head. Found in tide-pools on algæ.
PHYLUM =NEMATHELMINTHES=
ROUNDWORMS
The worms of this phylum have the general name of roundworms, which
distinguishes them from the flatworms of the preceding division and
from the segmented worms of the /Annulata/. The body is elongated,
cylindrical, smooth, and pointed at both ends. With few exceptions,
they are parasitic.
A few of the nematode species are free, living under stones and among
seaweeds at about low-water mark.
CLASS =NEMATODA=
GENUS ^Pontonema^
^P. marinum.^ Slender, white, smooth, active, cylindrical;
constantly coiling and uncoiling itself.
PHYLUM =ANNULATA=
SEGMENTED WORMS
The name of this phylum expresses the principal characteristic of
the group of worms which have elongated bodies composed of series
of short parts, or ring-like divisions. Each one of these segments
contains a separate and similar set of internal organs. [pg171]
The annelids are divided into four classes, one of which, the
/Gephyrea/, has not the characteristics which distinguish the group.
The classes are easily recognized by conspicuous features. Some have
bristles; others have scales; others have tentacles around the head
and inclose themselves in tubes. Many are highly colored, and all
are of great interest to the naturalist from the diversity of their
habits, form, and structure, and from the analogies they bear to
other and higher types of animals.
The annelids are the highest type of worms, their organs having
attained more special functions. The sense-organs of eye and ear
are more developed, and the nervous system has distinct centers,
or ganglia, the first and largest ganglion being a part of the
head. They are found in abundance everywhere. Some species grow to
the length of one foot or two feet. Some are carnivorous, others
vegetarian, and many are mud-eaters, swallowing sand and mud for the
sake of the organisms they contain. They themselves are food for
fishes, which devour them in vast quantities, rooting them out of
their burrows or capturing them at night, at which time they swim
about.
CLASS =CHÆTOPODA=
("/Bristle-footed/")
[Illustration: A magnified parapodium of /Nereis dumerilii/: /dors.
cirr./, dorsal cirrus; /vent. cirr./, ventral cirrus; /s/, setæ.]
The bristle-worms. This class of worms has bunches of bristles on
both sides of each segment of the body, which serve as organs of
locomotion, or bristle-feet. The bristles emanate from outgrowths
of the body known as /parapodia/, which are practically limbs. The
parapodia are sometimes divided into distinct lobes or branches. The
bristles are of various shapes and often of brilliant color. They
are usually horny, sometimes simple, sometimes divided into joints,
and vary in shape in different genera. The parapodia have, besides
the bristles, a second set of [pg172] hair-like appendages, called
/cirri/. These are sense-organs and also have a respiratory function.
The cirri too vary in shape in different genera. Generally they are
hair-like, but sometimes conical; again they are broadened into
scales, as in the /Aphroditidæ/.
The body-cavity in chætopod worms is divided into a series of
chambers or segments. These divisions seem on the exterior like
constrictions, and give the body the appearance of a series of rings.
The internal organs are repeated in each segment, so that each of
the latter contains a portion of the alimentary canal, a pair of
/nephridia/, a pair of nerve-ganglia, and blood-vessels which connect
the main blood-vessels running along the dorsal and ventral surfaces.
The alimentary canal runs through the body, but is constricted at
each joint. The nephridia are curved tubes, which are excretory
organs, opening to the outside and carrying off the waste products
which have passed into the fluid of the body-cavity.
The chætopod worms have a well-developed nervous system, beginning
with a two-lobed ganglion forming a brain and head, then extending
through the worm in a double ventral chain and series of ganglia.
They have also a blood-vascular system. The blood is either colored
or colorless. Sometimes it is a bright red or green, and is often
visible through the body-wall. The circulation is effected, not
by means of a heart, but by wave-like (peristaltic) contractions
of the dorsal blood-vessel. The body is cylindrical, but in many
cases is somewhat flattened. There are two layers of muscles, one
of which encircles the body, while the other extends parallel with
its length. Respiration is effected by /gills/, which may be simple,
hair-like appendages to the parapodia, or branched, or comb-like
in form. Sometimes they are confined to the middle segments, as
in /Arenicola/; sometimes to the segments near the head, as in
/Tubicola/; or they may be extended over the whole dorsal surface.
SUBCLASS =POLYCHÆTA=
("/Many-bristled/")
The polychæte worms have one or two well-developed parapodia, or
limbs, on each side of every segment of the body, and on each
[pg173] parapodium is a bunch of bristles, or /chætæ/. There are
hundreds of species of this class of worms, the species being based
on the shape and the lobes of the parapodia, the relative length of
the cirri, the form and arrangement of the chætæ, and so on. They
are abundant on the shore everywhere, but abound where rocks and
stones afford them some shelter. Many burrow in the sand and mud.
In doing this the worm eats his way into the hole, swallowing the
mud and sand. He assimilates the organic or vegetable matter the
mud contains, and ejects the rest in cylindrical coils, known as
castings, which lie in heaps at the mouth of the burrow. By these
castings they may be traced. Others secrete tubes.
The polychæte worms are divided into /Errantia/, which are wandering,
free-swimming forms, and /Sedentaria/ or /Tubicola/, which live in
tubes permanently. These distinctions are not strictly correct, since
some species of errant polychætes form tubes (/Eunicidæ/), and some
/Sedentaria/ form no tubes.
Many polychætes are beautifully colored, some in vivid reds and
greens, with various markings; some are iridescent; some are
phosphorescent.
ORDER =ERRANTIA=
Carnivorous, free /Polychæta/, with protrusible pharynx armed with a
horny jaw. "They are active, fierce beasts of prey."
FAMILY ~SYLLIDÆ~
This family is the highest in organization of the worms. They are
small, the majority being less than an inch in length, and many are
minute. They are often highly colored. Many have long cirri on the
feet; some have alternation of generation. They are common everywhere
along the coast, but are not seen unless searched for. Sponges
sometimes are alive with them. They are interesting subjects for
microscopic study.
FAMILY ~APHRODITIDÆ~
The scale-bearing annelids. This family of worms is distinguished
from all others by having scales on the back. The scales, called
/elytra/, are flattened dorsal cirri carried on the upper parapodia,
[pg174] and generally on alternate segments and in a double row down
the back. The elytra are the breathing-organs, and, although of a
horny texture, are richly supplied with nerves. The worms are short
and have a large protrusible pharynx armed with a double pair of
horny jaws.
GENUS ^Polynoë^
The species of /Polynoë/ are determined by the number of scales they
bear. They have a flattened short body with nearly parallel sides.
The bristles are of a bright golden color. The proboscis is large and
has four powerful jaws at the end and a circle of papillæ at the top.
They are sluggish in movement and are found under stones and in the
crevices of rocks. When disturbed they roll themselves into a ball.
^P. squamata.^ Twelve pairs of rough scales; color sandy-brown,
speckled; one inch to one and a half inches long; the broad, oval
scales overlap and entirely cover the body and head. Some /Polynoë/
when disturbed throw off every scale. Very common north of Cape Cod.
^P. sublevis.^ Twelve pairs of smooth scales; usually grayish-brown
in color, speckled with dark spots; iridescent; last pair of scales
more slender than the others; length one and a quarter inches,
breadth about one quarter of an inch.
[Illustration: /Polynoë squamata./]
GENUS ^Harmothoë^
^H. imbricata.^ Sixteen pairs of smooth scales; variable in color;
usually gray, speckled, or striped.
GENUS ^Aphrodite^
^A. aculeata.^ This polychæte, sometimes called the sea-mouse, is
one of the most beautiful of worms. It is brightly iridescent in
color, from its setæ, which form a fur-like coating over the dorsal
surface. It has fifteen pairs of scales, but they are hidden by
the numerous setæ. These bristles cover its sides and back. Some
are coarse and nearly an inch long, with sharp points, and are
barbed near the ends. They curve over the back like the quills of a
porcupine. The body is three to six inches long. It is broadest in
the middle and tapers to a point. They live in mud below tide-mark,
and may be found washed upon the beach after storms. [pg175]
FAMILY ~PHYLLODOCIDÆ~
[Illustration: /Aphrodite aculeata/, natural size: /c/, neuropodial
chætæ; /p/, palps; 1, iridescent bristles; 2, stiff chætæ; 3, felting
bristles of notopodium.]
These animals are commonly known as "paddle-worms," on account of
having leaf-like cirri, which they use in locomotion. The head is
long and bears four pairs of short and four pairs of long tentacles.
The body is long and depressed, sometimes two feet in length, usually
eight to twelve inches long. The general color is bright green and
iridescent. Found in tide-pools. Specimens are often found by digging
in sandy mud, or they may be obtained by placing old shells and other
material in a dish of sea-water. When the water becomes a little
stale, the worms of this and other families make their way to the
sides of the dish, where they secrete a colorless slime which holds
mud or any light matter that it may come in contact with. In this
condition, when lifted or disturbed, they crawl rapidly out of the
slime, and show to good advantage their elongate body, which is often
beautifully colored.
GENUS ^Phyllodoce^
[Illustration: /Phyllodoce paretii./]
^P. gracilis.^ Three inches or more long and one sixteenth of
an inch wide; large proboscis, with twelve longitudinal rows of
prominent [pg176] projections on the swollen base, its terminal
end smooth, with a circle of round projections at the orifice;
color green, with a row of dark spots down the center of the dorsal
surface and a fainter line of spots on each side at the base of the
parapodia. Found on the New England coast.
FAMILY ~NEREIDÆ~
GENUS ^Nereis^
[Illustration: Head of /Nereis pelagica/.]
Among the most common of the polychæte worms is the genus ^Nereis^,
various species of which are found in all parts of the world. They
are abundant under stones, among seaweeds, and living in burrows
between tide-marks. They are active, fierce, and voracious. Some
attain a length of eighteen or more inches. They are commonly known
as "clam-worms," and are used by fishermen for bait. /Nereis/ has a
distinct head, consisting of two parts. One, the /prostomium/, bears
on its upper side four eyes and a pair of short, conical tentacles,
and on the lateral sides a second pair of processes called /palps/.
The palps are more conspicuous than the tentacles, and consist of two
parts, a large base and a small terminal point, the latter capable
of being withdrawn. The palps are sense-organs and perhaps test the
food. The second part of the head, or /peristomium/, bears on the
sides four pairs of long tentacles which are used as feelers. The
mouth is on the ventral side, and through it /Nereis/ throws out
its pharynx, which contains a horny, notched jaw. It seizes its
prey with this jaw, which, with the pharynx, is then withdrawn and
tears the food apart, acting like a gizzard. The body of /Nereis/
is rounded above and nearly flat below. Each of the segments has a
pair of parapodia, bearing a bundle of bristles and cirri. The last
segment of the body is elongated, cylindrical, and without parapodia,
but has on the end a pair of long cirri, which give the appearance
of a divided tail. Each segment of the body, except the head- and
tail-segments, contains a pair of excretory tubes (/nephridia/),
ganglia of nerves, and a portion of the intestine and of the vascular
system. There are circular muscles by which the worm can diminish its
diameter, longitudinal [pg177] muscles in four bands, and muscles to
move the parapodia. Breathing is carried on over the whole surface
of the body, and especially in parts of the lobes of the parapodia
called gills. Its sense-organs are eyes, palps, tentacles, and cirri.
^N. virens.^ This species is found from New York northward in
muddy and shelly sand, and under rocks between tide-marks, living
in burrows, which it lines with a mucous secretion. It is very
active, and voracious, feeding on other worms, /Crustacea/, etc.,
which it captures with its horny, protruded jaw. At night it
leaves its burrow and swims freely about like an eel, frequently
falling a prey to fishes. In color it is dull bluish-green, with
some iridescence. The gills, which are leaf-like appendages on the
parapodia, are green on the anterior end of the body and become
bright red farther back. This species, and /N. branti/ of Alaska,
are the giants of polychæte worms, often measuring eighteen inches
or more in length.
[Illustration: /Nereis pelagica./ 1, male; 2, female.]
^N. pelagica.^ Found in abundance on the New England shore and
northern coasts under stones and on shelly bottoms. The female is
four to five inches long, while the male is only two inches in
length. In this species the body is widest in the middle, while in
other species it is widest at the anterior end. The palps are long,
and the second head-piece (peristomium) is twice as long as the
next segment. The color is reddish-brown and iridescent.
[Illustration: /Nereis limbata./ Male, anterior part of body, head
and extended proboscis.]
^N. limbata.^ Five to six inches long; jaws light yellow, sharp,
and slender; parapodia and bristles smaller on the anterior than on
the posterior end; color dark brown, with light lines on the sides
and appendages, pale red on the posterior end; dorsal blood-vessel
apparent, and the heart-like pulsations can be distinctly seen.
The male worm is red in the middle section. Found along the middle
Atlantic coast on sandy shores.
FAMILY ~NEPHTHYDIDÆ~
In this family the worms have a long, thick, flattish body, a section
of which has a quadrangular form. The lobes of the parapodia are
widely separated and fringed [pg178] with membrane, appearing like
double parapodia. The pharynx is very large and projected as in
/Nereis/.
GENUS ^Nephthys^
^N. ingens.^ Sometimes six inches long and one quarter of an inch
broad; usually smaller; color whitish, with red blood-vessel
showing on dorsal side; appendages dark blown; moves actively
and burrows quickly into the mud; when captured often breaks off
a portion of the posterior end, which it is able to reproduce;
proboscis large; branchiæ between the dorsal and ventral parapodia.
Found burrowing in all kinds of mud on the New England coast.
[Illustration: /Nephthys ingens./ Anterior part of body and extended
proboscis; ventral view. Enlarged.]
^N. picta.^ More slender than /N. ingens/; color whitish, mottled
with brown on the dorsal anterior end; often a dark line down the
back; head square in front and triangular in the back. Found in
sandy mud at low-water mark.
FAMILY ~EUNICIDÆ~
These are beautiful worms, having a reddish-brown iridescent body,
with bright-red branching gills, which look like feathers, along the
back. They form parchment-like tubes.
GENUS ^Marphysa^
^M. sanguinea.^ Length six inches or more; color bronze or
brownish-red and iridescent; has bright-red branched gills and six
caudal cirri of different lengths; body flattened, except at the
anterior end, where it becomes narrow and cylindrical; has powerful
jaws. It is found under stones and in clefts of rocks at low-water
mark, or more commonly in parchment-like tubes on shelly beaches,
from Cape Cod to New Jersey.
GENUS ^Diopatra^
^D. cuprea.^ This is one of the largest and most beautiful
annelids. It is found from Cape Cod to South Carolina at low-water
mark, in sandy mud-flats, living in long tubes which project above
the surface two or three inches and are hung with seaweeds and bits
of foreign matter. /Diopatra/ is twelve inches or more in length
and one half of an inch in breadth. In color it is reddish-brown,
specked with gray, and has a brilliant whitish or opal-like
iridescence. The appendages are yellowish-brown, specked with
green. The body is flattened. From the fifth segment long, dull
to bright red, much-branched gills, resembling plumes, [pg179]
extend nearly to the end of the worm. On the ventral side of the
parapodia are whitish tubercles with a dark spot in the middle.
These papillæ secrete the long, broad tube in which the worm lives.
The worm is difficult to capture, for when pursued it retreats
quickly into its tube, which is so large that it can easily turn
around within it. (Plate XLVIII.)
[Illustration: /Diopatra cuprea./ Head and anterior part of body,
showing part of the branchiæ; side view.]
GENUS ^Arabella^
^A. opalina.^ Body cylindrical, twelve to eighteen inches long,
one quarter of an inch wide in the middle, and tapers to the ends,
which are comparatively small; lateral appendages short; color
bronze, with brilliant, opal-like iridescence; head small, conical,
but blunt and without tentacles; four eyes in transverse row at the
base of the head; segments well marked; coils into spirals when
outside of its burrow. Found in compact sandy mud at low-water mark
on the New England coast.
GENUS ^Lumbriconereis^
^L. tenuis.^ Twelve inches or more long, and slender, like a fine
cord; bright red and somewhat iridescent; very fragile. Abundant
in sandy mud on the northern New England coast, and found from New
Jersey northward.
FAMILY ~GLYCERIDÆ~
These worms are long and smooth, with numerous segments. They taper
at both ends. The head is small, conical, sharply pointed, and has
four very small tentacles. The proboscis, or [pg180] pharynx, when
protruded, is very large and long, and appears too large for the
worm. The proboscis has four hook-like jaws. These worms burrow
rapidly and disappear almost instantly into the mud or sand.
[Illustration: /Glycera meckelii/, with pharynx everted.]
GENUS ^Glycera^
^G. americana.^ Color red or purple; has branched gills on upper
side of parapodia. Found from South Carolina to Cape Cod on sandy
and muddy shores and flats near low-water mark.
^G. dibranchiata.^ Has a simple gill on both sides of the
parapodia; about eight inches long and one quarter of an inch wide
in the middle; proboscis one inch long and wider than the body on
the upper end. Abundant from New Jersey to Cape Cod.
ORDER =SEDENTARIA=
THE TUBICOLOUS WORMS
Many of this order construct tubes in which they live permanently.
Some species of both /Sedentaria/ and /Errantia/ have habits
pertaining to the other. These worms are without a protrusible
pharynx and without jaws. The body is usually divided into two or
three sections by segments and appendages of different forms. They
have hair-setæ on a limited number of segments only, varying with the
species; the remaining segments have /uncini/, or hooked comb-like
rows of setæ, which are very small, but often crowded in bunches.
Uncini exist also on segments having hair-setæ. Parapodia are often
lacking on the posterior parts and are usually without cirri. The
gills are usually confined to the anterior end and are sometimes
represented by tentacles around the head. The different species have
characteristic tubes, formed by mucus secreted by epidermal glands.
Sometimes the mucus hardens, making a parchment-like tube; again it
cements together grains of sand, or bits of shell, seaweeds, etc.
Some species secrete [pg181] calcareous tubes; these are often found
on rocks, in coral, and in the shells of mollusks. The anterior end
of the body is more highly developed than the posterior end.
FAMILY ~SPIONIDÆ~
GENUS ^Nerine^
^N. agilis.^ Two to three inches long; slender; somewhat flattened
at the anterior end; head conical and sharp; the two tentacles
about one half of an inch long; four eyes; color reddish-brown,
light green on the sides; gills red; tentacles greenish-white. It
burrows with extreme rapidity and lives on exposed beaches near
low-water mark.
^N. coniocephala.^ Two and a half inches long, one sixteenth of an
inch in diameter; head conical; body flattened on the dorsal side,
round on the ventral side; has two long tentacles turned backward
and a membrane on the gills of the anterior segments; gills red;
bristles long and numerous.
FAMILY ~CIRRATULIDÆ~
Worms of this family have a cylindrical body, more or less attenuated
at each end; segments similar throughout; many segments with long,
filamentous cirri which act as gills; and a conical head. They live
in burrows.
GENUS ^Cirratulus^
[Illustration: /Cirratulus grandis./]
^C. grandis.^ Four to six inches long; head acute; segments
numerous, short, and distinct; color dull yellow, or orange,
to brown, often iridescent beneath; ventral surface somewhat
flattened. Numerous long, filamentous, red to orange-colored cirri
extend nearly the whole length of the body and act as gills. It is
common in sand and gravel at low-water mark from Cape Cod to New
Jersey. [pg182]
FAMILY ~TEREBELLIDÆ~
The body is cylindrical and largest on the anterior end; there are
one to three pairs of more or less branched gills on the anterior
end, and the ventral surface of the anterior segments is thickened by
glands which secrete mucus for tube-building. These gland-spaces are
called /shields/.
GENUS ^Thelepsus^
^T. cincinnatus.^ Two to four inches long; pale red; marked like
lacework on the back; gills have numerous unbranched filaments
arising separately in two transverse rows; tubes thin, transparent,
flexible, and hung with foreign substances; attached along the
whole length.
GENUS ^Amphitrite^
[Illustration: /Amphitrite ornata./]
^A. ornata.^ Twelve to fifteen inches long; flesh-color, reddish,
or brown; three pairs of red plume-like gills and numerous
flesh-colored tentacles around the anterior end; tentacles
constantly in motion and sometimes extended eight or ten inches;
tubes a quarter of an inch or more in diameter, and firm, being
composed of sand and mud. It is found under stones in mud, gravel,
and sand at low-water mark from Cape Cod to New Jersey, often
associated with /Cirratulus grandis/.
GENERA ^Polycirrus^, ^Chætobranchus^
[Illustration: /Polycirrus eximius./]
^P. eximius^, ^C. sanguineus^. These are two species of bright-red,
fragile worms, found under stones, in mud. They do not form
tubes. The first is a small worm, the second twelve to fifteen
inches long. Both have long, crowded tentacles extending in
every direction and distended as the blood flows into them. /C.
sanguineus/ has [pg183] tentacles sixteen inches in extent, and
branched gills on short pedicels on the back. They are common in
mud at low-water mark from Cape Cod to New Jersey.
FAMILY ~AMPHICTENIDÆ~
GENUS ^Cistenides^
[Illustration: /Cistenides Gouldii./ ]
^C. Gouldii^ constructs conical free tubes of grains of sand in
a single layer; body short and a little curved; head obliquely
flattened; two broad groups of golden bristles turned upward on
each side of the anterior end; one to two inches long; color
light red or flesh-color, mottled with red or blue. This is a
common worm, and its horn-shaped tubes are so plentiful as to
attract attention on sandy shores. They will repay examination
with a glass, so beautifully are they built. The worm has
bunches of golden bristles arranged in two rows close to the
flattened anterior end, which make a kind of operculum to the
tube. This feature makes the species easy to identify. The worm
is transparent; the internal organs showing through give it the
various bright colors. It is found on sandy and muddy shores from
New Jersey northward.
FAMILY ~MALDANIDÆ~
The tubes of these animals are formed of sand, a short portion
projecting, and are very abundant in certain places. There is a horny
plate on the upper surface of the head, and the skin on the sides of
the head is raised in folds. There is a funnel-like process at the
posterior extremity; gills are lacking. Some of the segments in the
middle of the body are longer than the rest.
GENUS ^Clymenella^
[Illustration: /Clymenella torquata./ /a/, head and extended
proboscis, front view; /b/, posterior end; /c/, entire animal, side
view, natural size.]
^C. torquata.^ Body long, composed of twenty-two segments; the
fifth segment has a collar-like fold; the caudal extremity is
funnel-shaped and edged with papillæ; both [pg184] the first and
the last three segments are bare, the rest have short bristles
above and hooks below; head has a prominent convex plate with a
raised border; worm pale red, with bright-red bands around the
segments, sometimes brownish. It constructs nearly straight tubes
of pure sand close to low-water mark in sheltered coves, and ranges
from New Jersey northward.
GENUS ^Maldane^
^M. elongata.^ Six to eight inches long, one eighth to one quarter
of an inch in diameter; body cylindrical, cut obliquely at both
ends; head bordered by a slight fold; color brown, with red blood
showing through. Found in sandy mud at low-water mark, in firm,
deep tubes of fine mud, on the New England coast.
FAMILY ~ARENICOLIDÆ~
GENUS ^Arenicola^
^A. marina.^ Five to ten inches long; brownish-green; body
cylindrical, thickest on the anterior end; anterior and posterior
ends without chætæ; twelve to thirteen pairs of branched red gills
on the central segments. It makes burrows eighteen to twenty-four
inches deep on sandy southern shores, and can be traced by castings
at the mouth of the burrow. Commonly known as "lugworm," and used
by fishermen for bait.
FAMILY ~SABELLIDÆ~
In this family the gills arise from two semicircular bases forming
the crown; the second lobe of the anterior extremity is reversed like
a collar; the gill-filaments have secondary processes, and the tubes
are flexible, composed of cemented mud or sand. Found under stones,
the tube passing around the stone and opening upward.
GENUS ^Sabella^
^S. microphthalma.^ Length of tube one and a quarter inches,
diameter one eighth of an inch; body olive-green, specked with
white; wreath of tentacles half as long as the body; tentacles pale
yellowish or flesh-colored, with transverse lines of darker color.
It is found on the southern New England coast.
FAMILY ~SERPULIDÆ~
This family forms white calcareous tubes. One of the dorsal
gill-filaments is flattened, forming an operculum, or cover, with
[pg185] which the tube is closed when the worm has withdrawn itself
inside. The tubes are commonly found attached to shells and rocks,
usually solitary, but sometimes in clusters, crossing and recrossing
each other on the surface of the shell or rock. Plume-like gills
are attached to the anterior end of the body. The color differs
in different species. These worms may easily be mistaken for the
mollusks /Vermetus/, which live in similar tubes of larger size,
growing in masses.
GENUS ^Serpula^
^S. dianthus.^ Tubes often three inches long and one eighth of
an inch wide, the fixed end coiled and contorted, free end with
circular opening; tubes often show circular ridges, marking periods
of growth; operculum funnel-shaped, the exterior striated and the
edge bordered with short processes; wreath of gills nearly circular
and divided into two symmetrical parts; color variable. It is found
in tide-pools, also on the under side of rocks at low-water mark,
either solitary or congregated in masses, and ranges from Cape Cod
to New Jersey.
GENUS ^Spirorbis^
^S. borealis.^ A minute calcareous tube, in a close, flat coil
attached on one side; easily mistaken for a minute gasteropod
shell; worm has an operculum and wreath of gills. Found on the
fronds of seaweeds, on shells, etc.
CLASS =GEPHYREA=
This class of animals, once placed near the holothurians, belongs
with the annelid worms on account of their mode of development,
their structure being entirely dissimilar. They are without segments
and without parapodia. The body-cavity is filled with fluid and is
traversed by connective tissue and fine muscular fibers. They are
subcylindrical animals which can retract the anterior end of the
body. The mouth is surrounded by tentacles, or by tentacular folds,
and is at the base of the proboscis. They live in fissures of rocks,
in sand, mud, rock, or coral, and in deep gasteropod shells. Their
distribution is general.
ORDER =SIPUNCULOIDEA=
GENUS ^Sipunculus^
^S. nudus.^ The body is cylindrical, a foot or more in length
when extended. It is divided into two portions. The anterior end,
to the [pg186] extent of one sixth of the entire length of the
worm, is capable of being withdrawn into the remainder of the body.
This portion is called the /introvert/. The introvert is retracted
by means of special muscles forming a sheath around the gullet
and connected at the other end to the body-wall about half-way
down the body. It is narrower than the rest of the body and is
covered more or less closely with small horny papillæ which turn
backward and overlap like scales. The rest of the body is divided
into longitudinal furrows and circular markings, giving it the
appearance of being divided into squares. These markings correspond
to muscles which lie beneath. The introvert, when retracted, leaves
at the opening a lobed and plaited fold of the integument, giving
the appearance of tentacles. When the introvert is expanded there
is a fringe-like funnel around the mouth. The body is covered with
a horny cuticle and has an iridescent luster. The animal lives
buried in the sand and feeds upon sand, deriving its nourishment
from the organisms contained therein. The sipunculoids pass so much
sand and mud through their bodies that they are said to modify the
mineral substances on the bottom of the sea, as earthworms do the
soil of the land.
GENUS ^Phascolosoma^
^P. Gouldii.^ Body cylindrical, a foot or more in length, a
quarter or half of an inch in diameter when expanded; but the
body constantly changes in size and shape as it is contracted or
expanded; surface of body parchment-like in texture and marked off
in small squares; color dull white to light brown. It is found on
the New England coast in sand and gravel at low-water mark.
IV
MOLLUSCOIDA
TABLE SHOWING THE CLASSIFICATION OF THE MOLLUSCOIDA DESCRIBED IN THIS
CHAPTER
Class =POLYZOA=
Subclass =Ectoprocta= (/Excretory opening outside lophophore;
mouth in center of circle of tentacles; tentacles retractile/)
Order =GYMNOLÆMATA= (/Circular lophophore/)
Suborder ~CYCLOSTOMATA~ (/Tubular calcareous zo[oe]cia,
with circular apertures devoid of closing apparatus/)
Set ARTICULATA (/Erect branches divided at intervals by
chitinous joints/)
Genera Species
^Crisia^ ^C. eburnea^
Set INARTICULATA (/Erect or adherent zoarium; unjointed/)
^Tubulipora^ ^T. flabellaris^
^Diastopora^ ^D. patina^
Suborder ~CHEILOSTOMATA~ (/Calcareous or chitinous
zo[oe]cia, usually with opercula; avicularia, vibracula,
and ovicells often present/)
Set CELLULARINA (/Flexible erect forms/)
^Ætea^ ^Æ. anguinea^
^Eucratea^ ^E. chelata^
^Cellularia^ ^C. ternata^
^Caberea^ ^C. Ellisii^
^Bugula^ ^B. turrita^
^B. Murrayana^
^B. flabellata^
Set FLUSTRINA (/Cells quadrate; front wall of zo[oe]cium
membranous or depressed, and has ridge-like margin/)
^Flustra^ ^F. membranacea^
^Membranipora^ ^M. pilosa^
^M. lineata^
^M. tenuis^
Set ESCHARINA (/Zo[oe]cium wholly calcified/)
^Escharella^ ^E. variabilis^
^Mollia^ ^M. hyalina^
^Cellepora^ ^C. scabra^
^C. ramulosa^
^C. pumicosa^
Suborder ~CTENOSTOMATA~ (/Horny or gelatinous zo[oe]cia,
having tooth-like processes which close the apertures when
the tentacles are retracted/)
^Alcyonidium^ ^A. ramosum^
^A. hirsutum^
^A. hispidum^
^A. parasiticum^
^Vesicularia^ ^V. dichotoma^
^V. custata^
Subclass =Entoprocta= (/Excretory opening within lophophore;
mouth near margin of area, which is surrounded by tentacles;
tentacles roll up instead of being retracted/)
^Pedicellina^ ^P. americana^
[pg190]
TERMS USED IN DESCRIBING POLYZOA
^Avicula´ria^: Specifically modified zo[oe]cia, resembling a bird's
head, found only in the /Cheilostomata/.
^Brown bodies^: Brown pigment-masses contained in the zo[oe]cia and
derived from the breaking down of the polypides.
^Lo´phophore^: The disk bearing the mouth and circlet of ciliated
tentacles.
^Orifice^: The open end of the zo[oe]cium.
^Ovicell^: The receptacle in which the eggs develop.
^Pe´ristome^: The ridge around the orifice of cell.
^Po´lypide^: The parts of the animal within the zo[oe]cium.
^Vibra´cula^: A lashing filament, or specifically modified zo[oe]cia,
found only in the /Cheilostomata/.
^Zoa´rium^: The whole colony.
^Zo[oe]´cium^: The body-wall of a single individual. [pg191]
POLYZOA
Among the numerous objects to be found on the beach at low tide
are the /Polyzoa/, of which there are said to be seventeen hundred
named species of the marine forms. These little animals, although
so plentiful, are inconspicuous, and it may be said that their very
existence is not known to those who are not professed naturalists;
yet they are easy to see, incrusting with a delicate calcareous
lacework the surface of stones and shells and seaweeds in the
tide-pools, and hanging from the rocks like branches of delicate
seaweeds. There is hardly a frond of even the fine red algæ on which
cannot be found the little tube holding shelly saucers, or the
creeping stems or branches of polyzoans. Any one of these little
masses, when examined with a pocket-glass, will surprise one with its
delicate and beautiful structure.
This class of animals is also called /Bryozoa/, and certain species
have the common names of sea-mats and corallines. They are broadly
divided into two groups, namely, the erect and the incrusting forms.
Those having tree- or plant-like shapes resemble seaweeds, while the
colonies which spread over stones, shells, and algæ resemble moss,
hence the name /Bryozoa/ (moss-animals). Both groups have the general
appearance of hydroids, because, like them, they are colonies having
plant forms and having their organisms inclosed in cup-like sheaths.
The resemblance, however, is but a superficial one, for the /Polyzoa/
have a much higher organization, each animal of the colony being a
separate and distinct individual. They can easily be distinguished by
the hair-like processes on the tentacles. The ciliated tentacles and
complete alimentary system are the conspicuous differences between
these colonies and those of the hydroids.
The /Polyzoa/ are very numerous and form a most attractive [pg192]
group. They are plentiful everywhere, occurring between tide-marks
and at great depths on the floor of the sea. Rocks protected from the
sun are often incrusted with the calcareous forms, while branching
species hang from the rocks and adorn rock pools. /Membranipora/,
in lace-like sheets, will be found on the larger seaweeds as well
as on various submerged objects. The beautiful little /Crisia/ may
be looked for on the fronds of red algæ, and /Alcyonidium/, in soft
moss-like patches, on /Fucus/. On some beaches are scattered the
sea-mats, /Flustra foliacea/, looking like bits of brown paper. A
pocket-lens will reveal the marvelous and orderly arrangement of the
two layers of cells, or zo[oe]cia, placed back to back. There is not
a more surprising object in the animal kingdom than a living branch
of /Bugula/. The cells on its spiral, profusely branched clusters
have appendages resembling a bird's head, with its bill constantly
opening and shutting. Of the erect polyzoans some are entirely
calcareous and rigid; such species live in deep water, and their
colonies are called corallines, as are also the calcareous algæ. They
have existed in vast numbers since early geologic times, and are
plentiful in the Tertiary deposits, known as Coralline Crags. Other
erect forms have a calcareous framework, which is not continuous,
but has horny intervals, so that the colonies are flexible and can
be swayed by the tides in shallow water where they live. Others
have complete horny exoskeletons. The same differences occur in the
incrusting forms, those on the seaweeds being either flexible, so
that they bend with the plant, or if entirely calcareous are so small
that they do not break when the plant sways to and fro. Still others
are gelatinous and resemble bits of sponge. The calcareous forms are
usually ornamented with ridges which form beautiful patterns.
The individuals of the polyzoan colonies are small polyp-like
organisms which have a cup-like inclosure of horny or of calcareous
substance, or of the two combined, as mentioned above. This inclosing
sheath is the exterior or cuticle of the animal and is called the
/zo[oe]cium/, the whole colony being called the /zoarium/. The animal
substance within the zo[oe]cium is the /polypide/, and consists of
the mouth, tentacles, and alimentary system. A disk at the anterior
end of the body, bearing the circle of tentacles, is [pg193] the
/lophophore/; it is a contractile body, being, with the tentacles,
protruded from the zo[oe]cium or drawn within it at will. In some
species the orifices of the zo[oe]cia are surrounded with spines;
others have lids, called /opercula/, which shut down when the
polypides are retracted. A singular modification of the zo[oe]cia is
seen in the genus /Bugula/, where peculiar shapes like birds' heads,
called /avicularia/, occur. In these singular appendages the upper
beak is hooked, while the lower one, or mandible, is the operculum of
the zo[oe]cium. These constantly open and shut by means of muscles,
and although their function is not certainly known, it is thought
that they capture prey. Other modifications are whip-like processes,
or flagellate filaments, called /vibracula/, which constantly
beat the water. In many of the zo[oe]cia of the colony there are
dark-colored masses, called /brown bodies/. These are formed by the
degeneration of the polypides, which at certain periods break down,
their tentacles and alimentary system ceasing to act and becoming
brown masses. The body-wall then puts out a bud internally and forms
a new polypide, which absorbs, or passes out, the brown body. The
term of life of a single polypide is not known, but in every colony
many such transformations are constantly taking place.
The colonies originally start from larvæ produced in the /ovicells/
of the zoaria. The ovicells are sometimes very large and pear-shaped,
occurring at intervals on the stems; or there may be one at the top
of each zo[oe]cium. They look like pearls. A larva, when liberated,
swims about for a time, then attaches itself to a fixed object, and
increases, by budding, into some one of the various forms which the
colonies take.
SUBCLASS =ECTOPROCTA=
ORDER =GYMNOLÆMATA=
SUBORDER ~CYCLOSTOMATA~
ERECT OR CREEPING POLYZOA
The zo[oe]cia are more or less cylindrical; the upper ends are
sometimes completely free and sometimes closely adherent. The
[pg194] opening of the cell has no operculum. Ovicells, containing
the embryos, appear like pear-shaped swellings.
GENUS ^Crisia^
[Illustration: /Crisia eburnea/; a branch bearing ovicells, highly
magnified.]
^C. eburnea.^ This species is found in tide-pools on algæ,
especially on the red seaweeds, growing in bushy tufts from one
half of an inch to an inch high. Calcareous, with horny joints;
cells in two rows, semi-alternate, cylindrical, free at one end,
bent; no operculum; ivory-white; ovicells large and pear-shaped.
Common from Long Island Sound northward and on the Pacific coast.
GENUS ^Tubulipora^
^T. flabellaris.^ This species is found attached to slender
branched algæ, in coral-like masses of long, crooked, tubular
cells united at the base and spreading into fan-shapes placed flat
against the fronds. It is sometimes one quarter of an inch in
diameter. On the same alga may often be found /Crisia/, /Mollia/,
and /Cellepora/. (Plate XLIX.)
GENUS ^Diastopora^
^D. patina.^ Tubular cells rise from a saucer-shaped disk about a
quarter of an inch in diameter; cells lie obliquely or stand erect,
and are crowded toward the center; margin of disk without cells;
colony white and calcareous. Found on algæ and eel-grass from Long
Island Sound northward.
SUBORDER ~CHEILOSTOMATA~
In this suborder the zo[oe]cia are either horny or calcareous, and
the orifices are usually surrounded with spines and have opercula.
The orifices generally have raised margins, or peristomes. Ovicells
form helmet-like coverings overhanging the orifices.
GENUS ^Ætea^
^Æ. anguinea.^ Delicate, white, creeping, calcareous stems, from
which rise numerous club-shaped cells, about one eighth of an inch
high, each one with an aperture in the end. This species creeps in
wavy lines along the fronds of algæ, and is frequently found on
/Dasya/, /Griffithsia/, /Plocamium/, and eel-grass.
[Illustration: PLATE XLIX. Tubulipora flabellaris. 1, Tubulipora
flabellaris, natural size. Eucratea chelata. Cellularia ternata. 1,
Cellularia ternata, natural size.]
[Illustration: PLATE L. Caberea Ellisii. Bugula turrita. 1, Bugula
Murrayana; 2, B. Murrayana, magnified; 3, B. Murrayana, a few cells,
more highly magnified; 4, B. flabellata; 5, B. flabellata, magnified.]
GENUS ^Eucratea^
^E. chelata.^ A small, delicate species rising from a creeping
stem. It has branches composed of single rows of horn-shaped cells
having an oblique aperture on the side. Found at extreme low-water
mark on hydroids, shells, stones, and /Fucus/. (Plate XLIX.)
GENUS ^Cellularia^
^C. ternata.^ Zoarium filamentous, spreading, about one inch high,
white, calcareous, branched in a forking manner; cells long,
narrowest at base, arranged in series of three and on the same
plane, apertures oblique and facing one way; horny joint between
each cluster of cells. This species grows in deep water from Cape
Cod northward, and is found on objects washed upon the beach.
(Plate XLIX.)
GENUS ^Caberea^
^C. Ellisii.^ Zoarium erect, with fibrous base, leaf-like, branches
in a forking manner; branches straight, stiff, narrow, spreading;
cells arranged in rows of three, adherent throughout; long bristles
emanate from near base of many cells; egg-capsules globular,
smooth, pearly. Common from Cape Cod northward in deep water.
(Plate L.)
GENUS ^Bugula^
[Illustration: 1, /Bugula turrita/, enlarged; 2, the same, a
branchlet, highly magnified; 3, the same, a branchlet, bearing
ovicells.]
^B. turrita.^ This is a very abundant species, found everywhere
along the coast from Maine to North Carolina. Large quantities of
it are [pg196] sometimes thrown upon the beach by storms. It
grows in erect tufts, sometimes a foot long, and is much branched;
the branches grow around the stem in a spiral manner, forming
dense clusters. The lower part of the stem is often naked (having
lost the branches) and bright orange in color, while the tufts of
branches at the top are pearly-white or yellowish. The cells are
long, with a long, pointed spine on the upper outer angle. Like all
species of /Bugula/, it has bird-head appendages, which can be seen
under a powerful glass. (Plate L.)
^B. Murrayana.^ Clusters of broad, thin, flexible fronds, one
to two inches high, attached by a slender base and spreading in
entangled masses; fronds wedge-shaped, flat, dividing in a forking
manner; outer cells have bristle-like filaments, which constantly
beat the water; all cells have avicularia, or bird-head appendages.
(Plate L.)
^B. flabellata.^ Fan-shaped fronds of flat branches, divided in a
forking manner; the cells are arranged in four or five longitudinal
rows, are oblong, with a spine at each side of the circular
aperture, and are capped with pearl-like ovicells. This species,
like others of the genus, bears the very singular structures known
as avicularia, or bird-head appendages. They show, under a strong
glass, a hooked beak, like that of the hawk or parrot. These beaks
are attached by flexible stems and are provided internally with
powerful muscles by which they are constantly opened and closed;
the beak can bite with considerable force. In this species they are
attached to the sides of the cells. (Plate L.)
GENUS ^Flustra^
^F. membranacea.^ This species forms gauze-like incrustations on
the fronds of seaweeds, and is common on /Fucus/ and /Laminaria/,
spreading irregularly over several inches of space. The cells are
oblong, quadrangular, with a blunt, hollow spine at each angle.
Many specimens have simple horny tubes, closed on top, rising from
some of the cells to the height of half an inch. (Plate LI.)
[Illustration: PLATE LI. Flustra foliacea. 1, 2, Cellepora pumicosa,
natural size; 3, C. pumicosa, magnified; 4, C. ramulosa. 1, Flustra
membranacea; 2, 3, F. membranacea, magnified. Vesicularia dichotoma.]
GENUS ^Membranipora^
^M. pilosa.^ An incrusting variety, composed of a single layer of
cells spreading irregularly over the surfaces of stones, shells,
and seaweeds, sometimes completely covering the fronds of /Chondrus
crispus/, /Phyllophora/, /Rhodymenia/, and other algæ. The cells
are membranaceous, with a calcareous rim, and have one long hair
and several small ones surrounding the large roundish apertures. It
is found in abundance on the shores from Long Island Sound to the
Arctic Ocean.
[Illustration: 1, /Membranipora pilosa/; a few of the cells seen
from above, magnified. 2, /Membranipora pilosa/; a single cell,
seen in profile.]
^M. lineata.^ Cells oblong, crowded, closely adherent; slender
spines on edge of aperture, which bend over and meet across it;
incrusts rocks and shells in broad, thin, radiating patches; cells
[pg197] much smaller and narrower than those of /M. pilosa/;
easily distinguished from that species by its manner of spreading
and the absence of the one long hair. Common from New Jersey
northward.
^M. tenuis.^ Common on pebbles, often covering their whole surface
with a lace-like incrustation of very small oblong cells having a
three-lobed aperture. Found in Long Island Sound and north to Cape
Cod.
GENUS ^Escharella^
^E. variabilis.^ This species forms calcareous incrustations on
shells or pebbles. The layers are thin, but eventually overlap one
another, and the incrustation sometimes becomes an inch thick and
resembles coral. The color of the living animal is dull red. The
species ranges from Cape Cod to South Carolina, and is abundant in
Long Island Sound.
GENUS ^Mollia^
^M. hyalina.^ Cells subcylindrical, irregular, transparent, smooth,
and more or less oblique. The species forms small circular disks on
algæ in tide-pools.
GENUS ^Cellepora^
^C. scabra.^ It forms branching, coral-like masses on slender red
algæ.
^C. ramulosa.^ Branches cylindrical, rough, dividing in a forking
manner, spreading, two to three inches high, calcareous; cells
urn-shaped, irregularly arranged, apertures contracted, long spine
on the outer edge. It is found in deep water attached to shells,
and in tide-pools, where it grows chiefly on /Sertularia/ and other
hydroids and on slender red algæ. It ranges from Long Island Sound
to Greenland. (Plate LI.)
^C. pumicosa.^ Cells urn-shaped, irregularly crowded together,
forming a conglomeration of porous, brittle masses, not exceeding
an inch in breadth, usually round when small, oblong and knobbed
when large; spine on outer margin of aperture. It incrusts stones
and the stems of /Fucus/. (Plate LI.)
SUBORDER ~CTENOSTOMATA~
GENUS ^Alcyonidium^
^A. ramosum.^ Twelve to fifteen inches high; much branched;
branches smooth, cylindrical, one third of an inch in diameter,
usually crooked; branches in a forking manner; color rusty-brown.
Abundant in shallow water, attached to rocks, from New Jersey to
Cape Cod.
^A. hirsutum.^ A species common on seaweeds, sometimes completely
covering them, forming dirty, straw-colored, thick, cartilaginous
crusts covered with numerous conical papillæ. These are the
cells, or zo[oe]cia; they are surrounded with spines. Circular
yellow spots occur over the surface, which are clusters of eggs.
A good pocket-lens will show the cells, laid in beautiful order,
and perhaps the extended tentacles. Found from Long Island Sound
northward. [pg198]
^A. hispidum.^ One of the most common species found incrusting
the fronds of /Ascophyllum/ at low-water mark. It forms fleshy,
brown, soft crusts of moderate thickness, and has spines scattered
over the otherwise smooth and glistening surface. The cells are
inconspicuous, and each one has five long rigid bristles. Habitat,
Long Island Sound to Greenland.
^A. parasiticum.^ It forms thin, earthy crusts on algæ and
hydroids. The surface is porous; the cells are distant and arranged
irregularly, and seem as if composed of sand cemented with mud.
GENUS ^Vesicularia^
^V. dichotoma^ (^Valkeria pustulosa^). This species grows in
clusters of crowded slender stems, which branch in a forking
manner, the branches dividing in different planes, making a
tree-like form one to three inches high. At the points where the
branches divide is a dark, opaque substance, and at these points
also the cells are crowded in clusters of spiral rows and are
greenish-brown in color. The dark spots are in marked contrast to
the white translucent substance of the rest of the stem, giving a
spotted aspect to the whole. (Plate LI.)
^V. custata.^ Delicate, thread-like, jointed stems, with slender
opposite branches; cells small and elliptical, arranged mostly
in clusters. Found creeping like a small dodder-plant over other
polyzoans, hydroids, and seaweeds.
SUBCLASS =ENTOPROCTA=
GENUS ^Pedicellina^
^P. americana.^ A very small species. Club-like zo[oe]cia rise
from slender, white, creeping stems; tentacles roll up instead of
retracting into the cups. Found on hydroids, other polyzoans, and
algæ.
V
ECHINODERMATA
Phylum
=ECHINODERMATA=
Classes
=ASTEROIDEA=
(/Starfishes/)
=OPHIUROIDEA=
(/Brittle-stars/)
=ECHINOIDEA=
(/Sea-urchins/)
=HOLOTHUROIDEA=
(/Sea-cucumbers/)
=CRINOIDEA=
(/Feather-stars and Sea-lilies/)
[pg201]
TERMS USED IN DESCRIBING THE STRUCTURE OF ECHINODERMS
^Abo´ral surface^: The side opposite the mouth.
^Ambula´cra^: Tubular feet used in moving.
^Ambulacral zones^: The five areas containing the rows of tube-feet.
^Ampul´læ^: Reservoirs or vesicles at the base of the tube-feet.
^Auricula´ta^: The larval stage of holothurians.
^Bipinna´ria^ or ^Branchiolaria^: The larval stage of starfishes.
^Dorsal surface^: The back of the animal, generally, but not
necessarily, the upper side.
^Exoskeleton^: Outside framework or support, differing from a true
skeleton which lies inside the body.
^Interambulacral areas^: The five areas between the ambulacral
zones.
^Larva^: The animal in a stage of development from the time it
leaves the egg until it reaches the complete form of the species.
^Madreporic plate^: A sieve-like plate of carbonate of lime.
^Oral surface^: The side on which the mouth is placed.
^Ossicles^: Calcareous plates which cover the body and form the
exoskeleton.
^Pedicella´riæ^: Small spines which have divided ends, like
scissors or forceps.
^Plu´teus^: The larval stage of sea-urchins.
^Po´lian vessels^: One to ten sacs arising from the ring-canal.
^Ring-canal^: The canal around the mouth.
^Spines^: Processes which rise from the surface of the animal.
^Stone-canal^: A calcareous tube leading from the madreporic plate
to the ring-canal.
^Suckers^: Sucking-disks on the ends of the tube-feet.
^Ventral surface^: The side opposite the dorsal surface.
^Water-vascular system^: A series of canals which conduct water
through the animal. [pg202]
ECHINODERMATA
The echinoderms, although their shapes are very unlike in the
different classes, have the same general internal structure, and
also other features which place them together in one group. They are
radiates (page 113) of the highest type; they have an exoskeleton;
and many of them are beset with spines, from which the name is given.
They have locomotor organs, the /ambulacra/, and a /water-vascular
system/ peculiar to themselves. Some have the very strange power of
casting off, and developing again, parts of the body.
The development from the egg to the adult is remarkable, and of
unusual interest to naturalists. The larval stage of echinoderms
is so unlike the mature animal that for a long time the larvæ were
thought to be another class of animals, and therefore were given the
names which they still retain.
In observing echinoderms it will be seen that the dorsal part is
carried uppermost by some, such as the starfishes and sea-urchins.
In the former the back is broad and extended; in the latter it is
curved and contracted. But in crinoids the back is carried downward
and is extended like a stalk; in the sea-cucumbers (holothurians)
the dorsal and ventral surfaces are parallel with the long axis of
the cylindrical body, instead of being on a plane with the mouth and
excretory opening. Owing to the unusual positions of the dorsal and
ventral surfaces, the terms /oral/ (mouth side) and /aboral/ (side
opposite the mouth) are generally used in describing these species.
The surface of the body is divided definitely by the ambulacra, the
/ambulacral zones/, and the /interambulacral spaces/, but differently
in the different classes. The movement of the animals is [pg203]
effected by means of the tube-feet, or ambulacra. These have suckers,
which are attached or released by the power of the water-vascular
system. The /madreporic plate/, which can be distinctly seen in
starfishes at the angle of two of the arms, is a calcareous porous
plate which opens into the /stone-canal/. This canal passes through
the body and opens into a circular tube which runs around the
mouth. A system of canals extends from this circumoral tube, or
/ring-canal/, and eventually one canal opens into each tube-foot.
Water, entering by the madreporic plate, passes through the various
canals and into the tube-feet, which it distends. When the feet are
pressed against a substance and the water is withdrawn, a vacuum is
formed, which causes the disk-ends of the feet to act like suckers.
When the feet are again flooded the hold is relaxed. Thus the animal
drags its body along with a slow, gliding motion. The madreporic
plate, being calcareous, is said to act as a filter, purifying the
water as it passes into the body, which it furnishes with oxygen as
well as with locomotive power.
[Illustration: Aristotle's lantern.]
A curious organ found in the /Echinoidea/ (sea-urchins) is called
/Aristotle's lantern/. It is a complicated arrangement, not fully
understood, having forty parts, and is connected with the alimentary
system. One of the parts is the mouth, over which five teeth project.
These teeth grasp and grind the food. The exoskeleton is composed
of plates of carbonate of lime, called /ossicles/, which cover the
surface of the body. The ossicles are of various sizes and shapes,
and are one of the determining features in classification. They may
be scattered spicules of lime, separated plates joined by connecting
rods, or overlapping plates; or they may be fitted together so as to
form a continuous shell. The starfishes are usually carnivorous, the
sea-urchins usually vegetarian, while the holothurians, after the
manner of worms, take in sand and mud, deriving their nourishment
from the organic particles contained in them. All echinoderms live in
the sea. [pg204]
TABLE SHOWING THE CLASSIFICATION OF THE STARFISHES DESCRIBED IN THIS
CHAPTER.
Class =ASTEROIDEA= (/Starfishes/)
Order =PHANEROZONIA= (/Ossicles not crowded; large marginal
ossicles; spines only on dorsal surface; pedicellariæ sessile/)
Families Genera Species
~PORCELLANASTERIDÆ~ ^Ctenodiscus^ ^C. corniculatus^
~ASTROPECTINIDÆ~ ^Astropecten^ ^A. articularis^
^Psilaster^ ^P. floræ^
^Luidia^ ^L. senegalensis^
^L. clathrata^
^L. alternata^
~PENTAGONASTERIDÆ~ ^Mediaster^ ^M. æqualis^
~ANTHENEIDÆ~ ^Hippasteria^ ^H. phrygiana^
~PENTACEROTIDÆ~ ^Pentaceros^ ^P. occidentalis^
^P. reticularis^
^Nidorella^ ^N. armata^
~ASTERINIDÆ~ ^Asterina^ ^A. folium^
^A. miniata^
Order =CRYPTOZONIA= (/Ossicles crowded; pedicellariæ stalked/)
~SOLASTERIDÆ~ ^Solaster^ ^S. endeca^
^S. decemradiata^
^Crossaster^ ^C. papposus^
~ECHINASTERIDÆ~ ^Cribrella^ ^C. sanguinolenta^
^Echinaster^ ^E. sentus^
~HELIASTERIDÆ~ ^Heliaster^ ^H. multiradiata^
~ASTERIIDÆ~ ^Asterias^ ^A. vulgaris^
^A. Forbesii^
^A. ochracea^
^A. gigantea^
[pg205]
CLASS =ASTEROIDEA=
THE STARFISHES
These animals are named from their star-shaped outline. Some have
five long, spreading arms diverging from a small disk, which is
hardly more than their point of union; others have a large body with
short arms, which are like angular projections of the body, giving
a pentagonal shape. Some genera have a greater number of arms than
others; /Solaster/ has eleven to thirteen, and /Heliaster/ (the
sun-stars, found on the west tropical coast) has thirty to forty.
[Illustration: Diagram of water-vascular system of a starfish: /a/,
madreporite; /b/, stone-canal; /c/, ring-canal; /d/, radial canals;
/e/, ampullæ; /f/, ambulacra.]
The mouth of the starfish is in the center of the ventral side. A
ventral or /ambulacral groove/ extends through each arm. In these
grooves the ambulacra, or tube-feet, are arranged in rows. The
/ambulacra/ are hollow, cylindrical bodies, each of which has a
sucker at one end, and is connected at the other end with a little
globular body, the /ampulla/. The ventral groove forms a ridge in the
body-cavity. It is called the /ambulacral zone/, and is formed by a
double row of elongated plates, which meet and form a raised line
along the middle of the inside of the arms, and appear like ribs;
between them lie the ampullæ. These plates are called the /ambulacral
ossicles/. Numerous other ossicles extend over the surface, buried
in the integument of the body, making a calcareous network, or
/exoskeleton/. The ossicles are connected by muscles so that the
animal is not rigid, but is able to bend the body and even creep
through comparatively small places. The ossicles are covered with
/spines/ of two kinds. The very minute ones are the /pedicellariæ/,
and have a jointed end which opens and shuts like a pincers. Their
principal use seems to be to remove waste matter or other substances
from the body, keeping it free and clean. The pedicellariæ are
arranged, in some species, in circles around the [pg206] bases
of the spines, and form groups over the dorsal surface. Examining
the backs of different starfishes with a strong magnifying-glass,
one will be surprised to see the varied grouping of the spines and
pedicellariæ. At the extremity of each arm is a red eye-spot, which
is sensitive to light, and a tube-foot, which has no sucker and which
is believed to act both as an olfactory and as a feeling organ. The
madreporic plate lies at the angle of two of the arms or rays. Water
filters through the madreporic plate and passes by the stone-canal to
the ring-canal around the mouth, and thence to the radial tubes, one
of which extends through each arm and is connected by a branch with
each tube-foot. At the base of each tube-foot there is a globular
reservoir, or ampulla. A valve connects the tube-foot and ampulla.
When the ampulla is contracted, water is forced into and distends
the tube-foot; when the ampulla is distended, it withdraws the water
from the tube-foot, thus acting like a suction-bulb. When water
is sent into the tube-feet they are greatly extended and are then
placed against an object. The water being then withdrawn through the
ampullæ, a vacuum is formed, and the suckers are tightly attached.
By the alternating movements of the ambulacra the animal is dragged
slowly along and moves with a gliding motion. It does not deviate
from a straight path, going over elevations or through depressions
without turning aside; its body conforms to the irregularities of
the road and never bridges over spaces. The stomach extends a little
way into the arms, and a short intestine leads to the excretory
opening in the center of the back. Starfishes are carnivorous and
voracious, and are particularly [pg207] destructive to oyster-beds.
The animal fastens itself to a bivalve, and protrudes a part of its
stomach, with which it envelops its prey and slowly sucks it out of
its shell. When feeding on small mollusks they take them into the
stomach directly. Starfishes regain by natural growth parts of the
body which may be lost. Sometimes the animal throws off an arm to
escape capture, and self-mutilation also occurs where unfavorable
conditions exist. Oystermen formerly were ignorant of the starfish's
wonderful powers of regeneration, and were in the habit of cutting
up those captured in their forks and throwing them overboard, thus
increasing the number instead of destroying their enemies, as each
arm with a piece of the body attached to it will, it is said, become
a new individual. This tenacity of life makes starfishes difficult
to destroy, and they are exceedingly plentiful in all seas. One
naturalist speaks of seeing on the coast of Maine a bed of starfishes
which extended several miles and covered the bottom so closely that
he picked sixty individuals off a small stone. On the northern
shores of the Pacific coast they abound in great variety, and some
are of unusual size. /Asterias gigantea/ of this region measures
two feet across. Another species, /Phyncopodia helianthoides/,
measures a yard in diameter, and has twenty or more arms. The most
common species of the Atlantic coast are /Asterias vulgaris/ and /A.
Forbesii/; the former ranges from Long Island northward, the latter
from Massachusetts to Florida. These are the species particularly
destructive to oyster-beds. /Asterias vulgaris/ sometimes grows to be
fifteen inches in diameter; from this, which is perhaps the largest,
are found starfishes of all sizes down to the very small /Cribrella/.
They inhabit all varieties of bottoms, from low-water mark to deep
water. They are not always abundant in the same place, but seem to
move about.
Some oystermen believe that the starfishes get into masses like a
ball and are rolled along by the tide. This idea comes from the fact
that an oyster-bed may be free from them one day and the next be
covered by these pests. To get rid of them the beds are swept over
with a tangle, which is an iron bar holding swabs of raveled rope.
The spines of the starfish are caught in the [pg208] tangle, and
often hundreds are brought up in one haul and are then killed by
steaming.
The anatomical system of the starfish is easily traced by cutting
off, with scissors, the skin from the dorsal surface of the disk, and
also cutting a slit down one of the arms. In the center of the body
will be seen the upper part of the stomach, a small star-like spot,
from which radiate five branches, which divide and lead into the
much-ramified, plume-like organs which extend through the arms. These
are the pyloric cæca, whose function is to secrete the digestive
fluids. The much-folded stomach occupies the greater part of the
central space, its large convolutions showing on top. The mouth
connects with the stomach on the ventral side. By turning back the
skin from the arm, small filiform processes can in some large species
be seen; these are the dermal branchiæ, or breathing-organs, which
may either project through pores in the skin between the ossicles or
be entirely retracted. If the pyloric cæca be laid back, one can see
the rib-like arrangement of the ambulacral ossicles, and also the
ampullæ, which lie between the ossicles on each side of the ridge. If
an ampulla be inflated and then pressed, the corresponding tube-foot
will be seen to extend. To follow successfully the water-vascular
system, beginning in the madreporic plate and extending through the
stone-canal to the ring-canal around the mouth and thence through the
arms, requires a strong glass and more skilful manipulation.
ORDER =PHANEROZONIA=
FAMILY ~PORCELLANASTERIDÆ~
GENUS ^Ctenodiscus^ (Plate LII.)
^C. corniculatus.^ Pentagonal; about two and a half inches in
diameter; the body flat, with wide marginal plates, giving a
flat edge to the rather long, pointed arms; madreporic plate
large; color greenish; ambulacra without suckers, seeming to be
adapted to pushing through soft mud rather than dragging over hard
surfaces. It lives in deep water on muddy bottoms and ranges from
Massachusetts to Greenland. When dredged the animal is usually
found to be filled with soft mud.
FAMILY ~ASTROPECTINIDÆ~
In this family there are only two rows of tube-feet; the rays end in
sharp points and have large ossicles on the margins. [pg209]
GENUS ^Astropecten^
^A. articularis.^ The body is flat and smooth; the rays sharply
pointed and conspicuously bordered with marginal ossicles and
fringed with short spines; two rows of ambulacral feet; color rich
purple. Found in shallow waters of South Atlantic coast on sandy
bottoms. (Plate LII.)
GENUS ^Psilaster^
^P. floræ.^ Diameter four to five inches; arms sharply pointed
and conspicuously bordered with large ossicles; body flat, with
smooth surface, the ossicles seeming like mosaic; bright pinkish
flesh-color. It occurs in deep water off the eastern coast as far
south as New Jersey.
GENUS ^Luidia^
This genus of starfishes is celebrated for its peculiar habit of
breaking in pieces when taken from the water, and therefore good
specimens are almost impossible to obtain.
^L. senegalensis.^ Twelve to fourteen inches across; arms long and
narrow, tapering to a point and fringed on the edges with spines;
surface rather smooth, showing the separation of the ossicles;
color almost white, with dark line running through the center of
each arm; usually nine arms. Found in shallow water on the coasts
of Florida and the Gulf of Mexico.
^L. clathrata.^ Four to five inches across; light-colored; with
a fringe of spines on the margins of the arms, which taper to
a point; two rows of ambulacra. It is found from New Jersey
southward, and is one of the most common starfishes on the sandy
beaches of North and South Carolina. (Plate LII.)
^L. alternata.^ Upper surface purplish, with irregular yellowish
bands on the arms; under surface yellow. Found in shallow water on
the Florida coast.
FAMILY ~PENTAGONASTERIDÆ~
GENUS ^Mediaster^
^M. æqualis.^ Body flat; the five rays equal or exceed in length
the diameter of the disk; margins have double row of large plates;
surface covered with granules, which are easily rubbed off; bright
red above, pale orange below; diameter four inches. Common on the
coasts of Oregon and California.
FAMILY ~ANTHENEIDÆ~
GENUS ^Hippasteria^
^H. phrygiana.^ This beautiful starfish lives in deep water, but
is sometimes thrown up on the beach, and ranges from Cape Cod
northward. [pg210] It has a large, pentagonal, bright-scarlet
disk, five to six inches in diameter, with arms rather long and
pointed. The upper side is raised and cushion-like, and is covered
with blunt spines; the margins have larger spines of the same
shape. The pedicellariæ are sessile and so long and large as to be
easily seen with the naked eye. (Plate LII.)
FAMILY ~PENTACEROTIDÆ~
GENUS ^Pentaceros^
^P. occidentalis.^ Pentagonal; eight to twelve inches in diameter;
ossicles a network of rod-like plates, with prominent spines at
the points of union; body inflated in the center and running in
wedge-like form to the ends of the rather long and narrow arms; the
upper lines of the ridges have spines more prominent than those
on the rest of the body; the spines of the larger specimens are
more like large warts or small hemispheres. Found on the Lower
California coast.
^P. reticularis.^ This starfish is the largest species on our
coasts. It is common in southern Florida close to the shore. The
body is three to four inches thick, flat on the oral surface, but
raised on the upper side, and tapers down in wedge-like form to the
points of the short arms. The prominent blunt spines which cover
its surface are arranged in a somewhat regular net-like order, and
the sharp-edged margins have an even row of larger spines of the
same form. The madreporic plate is nearly in the center of the
disk, and is quite conspicuous, being bordered with a circle of
small spines. Its color is dull yellow, and its size often a foot
or more in diameter. It is the large starfish so often seen in
curiosity-shops. (Plate LII.)
GENUS ^Nidorella^
^N. armata.^ This very curious pentagonal species, found on the
California coast, is five to six inches in diameter and red in
color. The upper surface is raised and covered with thick, pointed
spines one half of an inch to one inch long, arranged in lines, but
not crowded. The ossicles on the margins are large; some of them
are hemispherical and bear large spines. Smaller spines border the
under edge of the margins. (Plate LIII.)
FAMILY ~ASTERINIDÆ~
The starfishes of this family are pentagonal, with a large body and
short arms. The disk is more or less elevated in the center, and the
edges are sharp. There are two rows of ambulacra. The ossicles are
notched and overlapping. The family is confined to temperate and
tropical waters.
GENUS ^Asterina^
^A. folium.^ Small, pentagonal, swollen (gibbous). Found on the
Florida coast.
[Illustration: PLATE LII. Ctenodiscus crispatus. Astropecten
articularis. Luidia clathrata. Hippasteria phrygiana. Pentaceros
reticularis.]
[Illustration: PLATE LIII. Nidorella armata. Asterina miniata.
Solaster decemradiata. Crossaster papposus.]
^A. miniata.^ Pentagonal; somewhat raised in center; about one and
a half inches across; edges sharp. Found on the California coast
close to shore. (Plate LIII.)
ORDER =CRYPTOZONIA=
FAMILY ~SOLASTERIDÆ~
GENUS ^Solaster^
^S. endeca.^ Dark red in color; nine to eleven arms, which are
shorter than the breadth of the disk; diameter of disk about five
inches; two rows of ambulacra; surface rather smooth. Common on
the coast of Maine, and found from Cape Cod to Newfoundland below
low-water mark.
^S. decemradiata.^ This species is common on the North Pacific
coast. It has ten arms, which are about twice the length of the
diameter of the body, the whole body being about a foot across.
(Plate LIII.)
GENUS ^Crossaster^
^C. papposus.^ Twelve to fifteen arms, half as long as the breadth
of the body; upper surface an open network of calcareous rods,
or ossicles; at their points of union are club-shaped tubercles
bearing tufts of smaller spines; concentric lines and spots of red
and purple over the spiny upper surface; color light underneath.
Common on the New England coast. (Plate LIII.)
FAMILY ~ECHINASTERIDÆ~
GENUS ^Cribrella^
^C. sanguinolenta.^ This species is abundant north of Cape Cod and
is found of all sizes from half an inch to two inches in diameter
and of various colors--purple, orange, red, yellow, flesh-color,
etc. It has five round arms, generally about four times as long as
the breadth of the disk. The ends are often turned upward. It is
covered with crowded short spines, like little warts, which give
it a nearly smooth surface. It has two rows of ambulacra. It moves
with two of its arms turned forward, as if they were dragging the
other three behind them. Unlike most species, the young are not
free-swimming, but the eggs are carried around the mouth of the
mother, and the young are retained there until they are capable of
taking care or themselves. (Plate LIV.)
GENUS ^Echinaster^
^E. sentus.^ This species occurs close to shore in the waters of
Florida and is perhaps the most commonly observed species on the
beach. It extends as far north as New Jersey. It is purplish in
color, and about four and a half inches in diameter, with two rows
of ambulacra, five arms, and a surface rough with spines. [pg212]
FAMILY ~HELIASTERIDÆ~
GENUS ^Heliaster^
^H. multiradiata.^ Spines on the upper surface of rays in five
rows, but close to the disk proper become reduced to one row. Found
on the coasts of Lower California and Mexico. (Plate LIV.)
FAMILY ~ASTERIIDÆ~
The /Asteriidæ/ have the following characteristics: four rows
of tube-feet; ossicles small and unequal; spines isolated or
grouped; pedicellariæ of two forms, forceps-like and scissors-like
respectively. They include the very common forms found on all beaches.
GENUS ^Asterias^
^A. vulgaris.^ The common starfish of the Atlantic coast, from
Long Island Sound to Labrador. It occurs at low-water mark and
extends into deep water. It has five arms, which taper to a point.
Large specimens measure fifteen inches across. The upper surface
is rough, being covered with short spines, which are largest and
thickest at the edges of the rays, and surrounding them are the
pedicellariæ. The color varies from pink, yellow, and brown to
purple.
^A. Forbesii.^ The common starfish of the Atlantic coast, from
Massachusetts Bay to the Gulf of Mexico. This species resembles
very closely /A. vulgaris/, but can be distinguished from it by
the madreporic plate, which is bright orange, while in the former
it has the same color as the animal; also the arms are a little
swollen at the base and terminate more bluntly. These two species
are very destructive to oyster-beds, especially where their ranges
overlap. It is computed that they destroy annually two hundred
thousand dollars' worth of oysters. Vast numbers congregate where
the feeding-ground is good, and move in long lines from place
to place. The oystermen dredge over the beds and bring them up
in thousands, then steam them or throw them on the shore above
high-water mark. (Plate LIV.)
^A. ochracea.^ The common starfish of the Pacific coast, from
Sitka to San Diego. Five rays, each hardly twice as long as the
diameter of the body; spines running irregularly over the surface,
but forming a pentagon at the middle of the disk and inclosing the
madreporic plate; diameter eight inches. It is very common near San
Francisco on rocks at low-water mark. (Plate LIV.)
^A. gigantea.^ Body very large and swollen; six rays, somewhat
less in length than twice the diameter of the disk; aboral surface
covered with numerous short, blunt, equidistant spines of uniform
size and regularly distributed; spines contracted at the base and
striated; diameter two feet. Found on the California coast.
[Illustration: PLATE LIV. Cribrella sanguinolenta. Heliaster
multiradiata. Asterias Forbesii. Asterias ochracea.]
TABLE SHOWING THE CLASSIFICATION OF THE BRITTLE-STARS DESCRIBED IN
THIS CHAPTER.
Class =OPHIUROIDEA= (/Brittle-stars/)
Order =EURYALIDA= (/Skin without plates; arms simple or branched,
and capable of being rolled up/)
Genera Species
^Astrophyton^ ^A. Agassizii^
Order =OPHIURIDA= (/Skin with plates/)
^Ophiopholis^ ^O. aculeata^
^Amphiura^ ^A. squamata^
^Ophiocoma^ ^O. riisei^
^O. æthiops^
^O. Alexandri^
^Ophiothrix^ ^O. angulata^
[pg214]
CLASS =OPHIUROIDEA=
BRITTLE-STARS
The ophiurans, or brittle-stars, differ from the starfishes in having
the arms quite distinct from the body. In starfishes the arms are
extensions of the body, and the viscera extend partway into them,
while in ophiurans the body is a central disk, with the five narrow
arms attached to its margin. In form they suggest a spider, and
sometimes are called sea-spiders. The name brittle-star is also
descriptive, since they break off their limbs readily. The arms are
narrow, taper to a point, usually curl at the ends, and have no
ambulacral grooves, but are completely covered with bare calcareous
plates (except in the first order, where they have a skin and no
plates). The ambulacra are small spines without suckers, which
emanate from the sides or margins of the arms and do not serve for
walking. The madreporic plate is on the ventral surface, in one of
the circular shields which surround the mouth. The alimentary canal
ends blindly. The egg-sacs lie between the arms and open by slits on
the under side, close to the arms, where they join the disk. Water
flows in and out of these pouches, which are thought to have also
respiratory and excretory functions. No eye-specks have been found,
but they must exist, since the animal is sensible to approaching
danger and quickly retreats. The ophiurans are more active than
starfishes, moving by wriggling, and clambering with their arms. They
are shy and hard to find, and it is difficult to capture a whole one,
since they throw off pieces of their arms at the least alarm. Often
they completely dismember themselves, an action which does them no
permanent injury, since they reproduce lost parts. They are more
commonly inhabitants of deep than of shallow waters, and are brought
up from the bottom in dredges in great numbers. [pg215] Some species
may be found near low-water mark under stones and in clusters of
mussels, and often in seaweeds, thrown up from deep water, on the
shore.
ORDER =EURYALIDA=
GENUS ^Astrophyton^ (Plate LV.)
^A. Agassizii.^ This very singular ophiuran is commonly called the
basket-fish, from its resemblance to a basket when the tentacles
are rolled up. Its body is covered with skin instead of calcareous
plates. The body is thick and somewhat circular in form, with
elevated radiating ridges on the upper side, and the skin is marked
off in star-like divisions. From the margin of the body extend
five arms, which at once divide in a forking manner; each section
again divides, and this division in pairs (dichotomous division)
continues until the ends of the arms have become very numerous and
attenuated. The arms are carried curled up or straight at will. In
moving, the animal seems to walk on these branches as if on tiptoe,
and in this position it forms a kind of net which entraps prey. The
arms and prominent parts of the disk are yellow, and the depressed
or membranous parts brown. /Astrophyton/ is six to eighteen inches
in diameter. It is found off the northern New England coast.
ORDER =OPHIURIDA=
GENUS ^Ophiopholis^
^O. aculeata.^ This is a common species, found in shallow water
on the North Atlantic coast. A similar or perhaps identical
species occurs on the North Pacific coast. It is spotted purple or
variegated in color. The upper surface of the body is covered with
plates variously arranged, sometimes in the shape of a star, and
each one is surrounded with small spines. The under side of the
egg-sacs is covered with small spines. These sacs open by slits on
each side next the arms, and have a rounded appearance, bulging
out between the arms. The arms, which are long and attenuated at
the ends, have on the upper side transverse oval plates surrounded
by a border of flat, roundish granules. Sometimes the plates are
divided into two or three pieces, when they are similarly bordered
with granules. The arms are fringed with rows of thick, compressed,
obtuse spines, generally six in each row. The under sides of the
arms have large quadrangular plates slightly separated from one
another and extending across the whole surface in regular, even
rows. (Plate LV.)
GENUS ^Amphiura^
^A. squamata.^ This very delicate species, found on shelly bottoms
below low-water mark from New Jersey northward, has a body less
than one quarter of an inch in diameter, with arms two inches or
more [pg216] in length and thread-like in size. These long,
slender arms have, on both the upper and under surfaces, a row of
overlapping plates, and are fringed with small spines, three in a
row. The color is gray or whitish, sometimes marked with darker
gray or brown. (Plate LV.)
GENUS ^Ophiocoma^
^O. riisei^, ^O. æthiops^, ^O. Alexandri^. These animals have
long spines on the sides of the arms, which give them a bushy
appearance. The surface of the body is granulated, but the arms
are covered with wide plates. Their color is brown above and light
beneath. /O. riisei/ is found at Key West, the other two species on
the coast of Lower California. (Plate LV.)
GENUS ^Ophiothrix^
^O. angulata.^ Body covered with short, rough spines; egg-sacs
conspicuous and extend like lobes between the arms; rays narrow and
thickly beset with long spines, which are serrated on the edges and
ends. Found on the Florida coast. (Plate LV.)
[Illustration: PLATE LV. Astrophyton. Ophiocoma æthiops Ophiothrix
angulata. Ophiopholis aculeata. Ophiocoma Alexandri. Amphiura
squamata.]
[pg217]
TABLE SHOWING THE CLASSIFICATION OF THE ECHINOIDEA DESCRIBED IN THIS
CHAPTER
=Class= =ECHINOIDEA=
Order =DESMOSTICHA= or =REGULARIA= (/Shell usually globular; mouth
and anus polar; lantern of Aristotle present/)
Families Genera Species
~CIDARIDÆ~ ^Cidaris^ ^C. tribuloides^
^Dorocidaris^ ^D. papillota^
^D. Blakei^
^Porocidaris^ ^P. sharreri^
~ARBACIADÆ~ ^Arbacia^ ^A. punctulata^
^C[oe]lopleurus^ ^C. floridanus^
~DIADEMATIDÆ~ ^Diadema^ ^D. setosum^
~ECHINOMETRIDÆ~ ^Echinometra^ ^E. subangularis^
^Strongylocentrotus^ ^S. drobachiensis^
^S. purpuratus^
^S. franciscanus^
~ECHINIDÆ~ ^Echinus^ ^E. gracilis^
^Toxopneustes^ ^T. variegatus^
Order =CLYPEASTROIDEA= (/Corona or shell a more or less flattened
disk; anus excentric; lantern of Aristotle present/)
~ECHINANTHIDÆ~ ^Clypeaster^ ^C. ravenellii^
^Echinanthus^ ^E. rosaceus^
~SCUTELLIDÆ~ ^Echinarachnius^ ^E. parma^
^E. excentricus^
^Mellita^ ^M. testudinata^
^Encope^ ^E. michelini^
Order =SPATANGOIDEA= or =PETALOSTICHA= (/Heart-shaped; mouth and
excretory opening excentric; no lantern of Aristotle/)
~SPATANGOIDÆ~ ^Moira^ ^M. atropos^
^Lovenia^ ^L. cordiformis^
^Schizaster^ ^S. fragilis^
^Metalia^ ^M. pectoralis^
^Brissopsis^ ^B. lyrifera^
[pg218]
CLASS =ECHINOIDEA=
SEA-URCHINS, CAKE-URCHINS, HEART-URCHINS
ORDER =DESMOSTICHA=
SEA-URCHINS
The shell of a sea-urchin consists of many calcareous plates,
or /ossicles/, fitted closely together and forming a continuous
exoskeleton. The plates are so united that externally the marks of
juncture are not perceptible, but on the interior the shape of these
plates is well defined. In examining such a shell, or test (they
abound on the beach), it will be seen that its surface is covered
with numerous hemispherical projections or knobs, which are grouped
in double rows and run in meridional lines from one pole to the
other of the more or less spherical body, separating it into ten
divisions. Five of these divisions have perforations, or small pores
in the plates of the shell, and are called the /ambulacral zones/
or areas, because through these pores pass the small tubes, in the
living animal, which connect the tube-feet, or /ambulacra/, with the
radial water-canals and the /ampullæ/ (see page 206). The wide spaces
between these double rows of pores are called the /interambulacral
zones/ or areas. The ten spaces diverge from the /peristome/, or
soft part around the mouth, in the center of the lower surface, and
converge in the small area at the top or aboral side. In the center
of this small circular dorsal space is the excretory opening, and
surrounding it are ten plates, five of which have openings into the
egg-sacs. One of them is larger than the others, and is modified to
form the /madreporic plate/. The other five plates have eye-specks.
The ambulacral zones terminate at these ocular plates.
The numerous spines which cover the animal are of three [pg219]
kinds, and proceed from the knobs on the exoskeleton, over which they
fit, forming ball-and-socket joints, which enable them to move in
any direction. The long spines are ribbed, and seem to have no other
function than that of protection. The second set, the /pedicellariæ/,
are very peculiar small organs scattered over the surface in great
numbers, and consisting of a head bearing three bill-like blades
mounted on a long, flexible stalk. The office of some of the
pedicellariæ is to remove waste from the excretory opening; this is
passed down regular lines and dropped into the water, thus keeping
the body clean. Others are constantly opening and shutting their
forks, reaching in all directions and grasping and removing anything
which may have become entangled in the spines. They also capture
floating bits of seaweed, which they drag over the body to conceal
it. A third set of projections are the /sphæridia/, small globular
bodies said to be connected with perception.
[Illustration: Test of sea-urchin, with the spines removed to show
the arrangement of the plates, lateral view: /Amb/, ambulacral zone
with its perforated plates; /Ap/, apical (aboral) pole; /Int. amb./,
interambulacral zones. (From Bronn's "Thierreich.")]
The spines vary greatly in size, number, and form in different
species, and are such conspicuous features as to make the
identification of species easy. In some the spines are solid and
fluted; [pg220] in others they are hollow, sharp, and brittle; again
in others they are short and silky, or very long and serrated, and so
on. In one species they are so broad and flat as to resemble little
sails. (See /Dorocidaris/.) (Plate LVI.)
The mouth, over which five long teeth project, is a part of
Aristotle's lantern, which forms a curious and prominent feature in
the center of the lower surface. Ten tentacles, like large tube-feet
without suckers, lie around the mouth. The alimentary canal, starting
in Aristotle's lantern, winds in two and a half coils around the
inside of the shell, supported by mesenteries, and terminates in the
excretory opening on the aboral surface. The sea-urchin has also
a water-vascular system similar to that of starfishes (page 206).
When the tube-feet are distended they project beyond the spines, and
enable the animal to move slowly about; but sea-urchins are less
active than starfishes, and although they are so well protected by
spines and have few enemies after maturity, they lie in sluggish
idleness in secluded places, and for further concealment often cover
themselves with seaweeds or stones.
The sea-urchin has a nervous system, which starts in a ring around
the mouth, ramifies through the body, and terminates in the
eye-plates. The tube-feet and all the spines are under nervous as
well as muscular control. Egg-sacs lie under the apex of the shell
and open by separate ducts into the five plates on the small upper
disk. Through these the eggs are discharged into the water, where
they become free-swimming larvæ, called /Pluteus/. This immature
sea-urchin (Pluteus) undergoes several curious transformations in
the course of its development, and does not in any way resemble the
mature animal. In spring the apical disk of the females will often
be found covered with orange-colored ova, and that of the males with
white sperms. In the growth of the animal, in its mature form, the
shell enlarges by accretions of lime on the individual plates, or
ossicles, of the exoskeleton, and by new plates formed around the
apical disk. Sea-urchins are compared to starfishes folded over, the
eye-specks on the ends of the rays meeting in a small area around
the excretory opening, the ambulacra following spherical lines and
leaving the mouth, as before, on the ventral side. [pg221]
The /Echinoidea/ present great differences in shape, being more or
less spherical, oval, discoid, and heart-shaped. These variations are
associated with the differences of internal structure, the openings
of the digestive tract being at the opposite poles in the spherical
and oval forms, but excentric in the disk- and heart-shaped species.
The sea-urchins are grouped in three orders in accordance with these
variations. All are characterized by the absence of arms, by having
the calcareous plates immovably united to form a firm test, and by
the great development of the movable spines upon the plates.
Sea-urchins are sometimes called /sea-eggs/, perhaps from their
shape, but possibly from the edible quality of some species, which
are eaten by the natives of the shore, who take them at the spawning
season, when the egg-sacs are distended. They are gregarious, and
frequently are so crowded together as literally to pave the surface
of rocks and the bottoms of tide-pools in sheltered places. The
following is quoted from A. Agassiz: "Many of the /Desmosticha/
along coasts exposed to the action of the waves live in cavities
which they hollow out of the solid rock. This they do, not by means
of any solvent, but by mere mechanical action. They chisel out with
their teeth the solid rock by incessant turning round and round, and
keep their cave, where they are frequently prisoners for the rest
of their existence, up to the size required by the growth of their
test and spines, by constant gnawing. On the coast of California the
common /Strongylocentrotus purpuratus/ occurs in this way. We find
long tracts of shore, where this sea-urchin is common, completely
honeycombed and pitted by cavities and depressions in which they seek
shelter against the powerful surf continually beating against the
rocks. The same species does not excavate in sheltered places, where
the sea-urchins can find protection between the interstices of large
fragments of rock or ledges more or less sheltered from the more
direct action of the open sea."
Sea-urchins in cavities of granite rock, where the openings are too
small for the animal to get out, are to be seen in thousands on the
coast of France at Croisic, Lower Loire. Spines of large sea-urchins
are used as slate-pencils by the missionaries in the Pacific
Islands. [pg222]
FAMILY ~CIDARIDÆ~
GENUS ^Cidaris^
^C. tribuloides.^ Similar to /Porocidaris sharreri/, but with
thicker and stouter spines. Found from South Carolina to Brazil.
GENUS ^Dorocidaris^
^D. papillota.^ A deep-water species which occurs off Chesapeake
Bay and southward. It has slender spines with distinct longitudinal
rows of serrations, and the spines are grouped in rosette-like
forms over the small spherical body.
^D. Blakei.^ This species is very peculiar in having broad,
fan-shaped spines; vermilion in color. Found in deep water in the
Bahamas and West Indies. (Plate LVII.)
GENUS ^Porocidaris^
^P. sharreri.^ This species occurs, in deep water, off the coast of
North Carolina and thence southward to the West Indies. The shell
is light greenish-pink. The spines are white, with brownish-pink
at the base, pointed, three and a half inches long, and surrounded
at the base with small, flat, triangular, secondary spines. (Plate
LVII.)
FAMILY ~ARBACIADÆ~
GENUS ^Arbacia^
^A. punctulata.^ A small species found in shallow water on shelly
and gravelly bottoms from Massachusetts to Mexico, and common
in Long Island Sound. The shell is about one inch in diameter;
the spines are rather thick and one half to three quarters of an
inch long. The color varies from deep violet--almost black--to
straw-color, and the spines are tipped with brown. The South
Carolina species are usually brick-red in the bare interambulacral
spaces, with darker sutures, and spines tipped with same color. The
animal walks by means of its spines, with a tilting motion, and
advances quite rapidly. (Plate LVII.)
GENUS ^C[oe]lopleurus^
^C. floridanus.^ This beautiful sea-urchin is taken on the Florida
reefs. The very brittle spines are one to four inches long, and
are banded with carmine and white. The shell has zones of light
chocolate-color alternating with orange and yellow.
FAMILY ~DIADEMATIDÆ~
GENUS ^Diadema^
^D. setosum.^ Spines very brittle, and from one to two and a half
inches long; jet-black. Found on the Florida reefs. (Plate LVII.)
[Illustration: PLATE LVI. Pedicellariæ of sea-urchins. Spines of
sea-urchins.]
[Illustration: PLATE LVII. Porocidaris sharreri. Dorocidaris
Blakei. Arbacia punctulata. Diadema setosum. Strongylocentrotus
franciscanus.]
FAMILY ~ECHINOMETRIDÆ~
In this family the ambulacral plates have several pairs of pores.
GENUS ^Echinometra^
^E. subangularis.^ This species, which ranges from South Carolina
to Brazil, and is also found in Bermuda, is common on mud-flats
and is easily distinguished by its oblong or elliptical shape.
Its shell is about three inches long in its widest portion. The
spines are one half of an inch to one inch long, thick at the base
and tapering to a point. The color is dark purplish-green to deep
violet--almost black.
GENUS ^Strongylocentrotus^
^S. drobachiensis.^ This sea-urchin (which bears, perhaps, the
longest name in technical nomenclature and has no other, unless
that of "sea-egg," which is applied indiscriminately to all
sea-urchins) is a very common species in shallow waters of the
northern temperate zones. It extends as far as New Jersey on the
Atlantic and to the State of Washington on the Pacific coast.
Although it is found as far south as New Jersey, it is there rare
and small; but farther north, especially on the coast of Maine,
it is exceedingly abundant. It is green or greenish-purple in
color, and resembles somewhat a large chestnut-bur. The body is
circular, somewhat depressed (but of variable thickness), and
about two inches in diameter. The spines are moderately slender
and longitudinally striated. It feeds partly on diatoms and other
small algæ, which it cuts from the rocks with its sharp teeth. It
also devours dead fishes, bones and all, and in return is swallowed
whole by the wolffish and other large fishes. It moves by means
of the tube-feet on its oral surface, slowly dragging itself
along, and frequently is seen with seaweed, a stone, or some other
substance on its back, which it places there with its pedicellariæ
for the purpose of concealment.
^S. purpuratus.^ The common purple sea-urchin of the west coast,
from Sitka to Lower California, found in abundance on the rocks
just beyond low-water mark. It is about one and a half inches in
diameter, with rather thick, pointed, and fluted spines.
^S. franciscanus.^ This is the largest species of the west coast,
the shell measuring sometimes five inches across, and the thick
spines one and a half inches in length. The tubercles on the naked
shells are very prominent, and the zones are very clearly marked.
It is purple in color and is often found in great quantities at
low-water mark. It ranges from Alaska to Lower California. (Plate
LVII.)
FAMILY ~ECHINIDÆ~
In this family the ambulacral plates have but three pairs of pores.
[pg224]
GENUS ^Echinus^
^E. gracilis.^ This is a deep-water species, which occurs from
Cape Cod southward. The shell is nearly spherical, but is a
little depressed on the oral side, and has twenty bands of color,
alternately green and white. The spines are short and thin.
GENUS ^Toxopneustes^
^T. variegatus.^ This is the common species of the Southern States,
from North Carolina southward, and is found in shallow water in
protected places. The shell is nearly globular; the spines vary in
thickness and color, some being long, slender, and greenish, while
others have stout and blunt spines of a yellowish or violet tint.
ORDER =CLYPEASTROIDEA=
CAKE-URCHINS
The animals of this order, commonly known as sand-cakes or
sand-dollars, are flat and circular like disks. Sometimes they are
cut at intervals on the margin; again they have slits through the
body (/lunules/). They have a well-marked star-shaped figure on the
dorsal surface. This figure is formed by the ambulacra, or tube-feet,
which run in five rounded or petal-shaped lines on the under surface.
The mouth, in Aristotle's lantern, is in the center of the somewhat
concave ventral surface, the petal-like ambulacral zones meeting at
the central space. The excretory opening is on the margin of the
disk, at a point between two of the sections of the star-like figure.
This marks the posterior part of the body, while the opposite arm
of the star marks the front or anterior end. The spines are very
fine and silky, and are spread abundantly over the whole animal.
Clypeasteroids are mainly found in sand considerably below low-water
mark, though some species thrive where they are exposed to the surf
on open sandy beaches.
FAMILY ~ECHINANTHIDÆ~
GENUS ^Clypeaster^
^C. ravenellii.^ This species occurs in deep water from South
Carolina southward. The disk is about four inches in diameter,
and is raised [pg225] in the center into a large cone. The
ambulacra run down the sides of the cone in straight lines, and
around the base is a depressed area which emphasizes a thick border
which extends around the scalloped margin. The color is light
yellowish-brown. (Plate LVIII.)
GENUS ^Echinanthus^
^E. rosaceus.^ This is a large species, oblong in shape, about
four to five inches across and much rounded on top, the body being
about two inches thick. The ambulacral zones are depressed, leaving
prominent elevations which make a very conspicuous figure on the
top. The color is light chocolate-brown. Found close to the shore
off the coasts of Florida, South Carolina, and the West Indies.
FAMILY ~SCUTELLIDÆ~
GENUS ^Echinarachnius^
THE SAND-DOLLARS
^E. parma.^ This species, the shells of which are very common
objects on sand-beaches from New Jersey northward, is generally
known as the sand-dollar. The animals have flat circular disks
about three inches in diameter. The ambulacral zones, in five
petal-like lines, form a distinct figure on the upper surface. The
mouth is in the center of the ventral surface, and the excretory
opening is on the edge of the disk. In life they are covered
with short, fine, silky spines, which seem like hair, and are
purplish-brown in color, but turn green when taken from the water.
The sand-dollars are exceedingly abundant off Nantucket Shoals,
where the bottom seems paved with them. They are eaten in great
numbers by flounders, cod, and haddock. When put in alcohol they
stain it a dark color. Fishermen prepare an indelible ink by
grinding to powder these animals and mixing it with some liquid.
This species is also found on the northern Pacific coast.
[Illustration: /Echinarachnius parma/, the sand-dollar. Much
smaller than natural size.]
^E. excentricus.^ This is the common sand-dollar of the Pacific
coast. The disk, instead of being circular as in /E. parma/, is
somewhat straight across the posterior end, and the posterior
ambulacral zones are shorter than the other three. The upper side
of the disk is raised, forming a cone-like elevation, the apex
being the center of the figure.
GENUS ^Mellita^
^M. testudinata.^ The disk is rounded in front and straight in the
back. Four long, narrow lunules, or cuts, occur on the sides in
line with the ambulacral, petal-shaped zones, but do not extend
quite to the edge of the disk; and a wide lunule occurs in the
interambulacral space [pg226] of the posterior end. The three
anterior zones are shorter than the posterior pair. On the upper
side of the disk the spines all turn toward the periphery. The
color of the living animal is greenish-blue. It is very abundant
from Cape Hatteras southward in shallow water, and the shells are
sometimes found as far north as Cape Cod. (Plate LVIII.)
GENUS ^Encope^
^E. michelini.^ Ambulacral zones unequal in size, the posterior
pair usually longer than the others; lunules like notches in the
margin, with a large one opening between the posterior ambulacral
zones nearly in the center of the disk; disk rounded in front and
square at the back. Common on the coasts of southern Florida and
the Gulf of Mexico in shallow water. (Plate LVIII.)
ORDER =SPATANGOIDEA=
HEART-URCHINS
The /Spatangoidea/, or heart-urchins, have heart-shaped or thick
elliptical bodies. The mouth and excretory opening are both away from
the center and on the ventral side. These animals seem deformed, so
much are they out of symmetry and so different in outline from the
other orders of the class. The ambulacral zones are in circles, or
petaloid in outline, as in cake-urchins, but are not continuous, and
the anterior one is usually unlike the others and frequently without
pores. The entire body is covered with spines, and these are the
chief organs of locomotion; the greater part of them turn backward,
giving the living animal the semblance of a porcupine. The mouth is
protected by a projecting plate, but Aristotle's lantern is absent
in this order. The anatomy is in general the same as in the other
orders, but the organs are turned in conformity with the inclosing
shell. Most of these animals bury themselves in sand or mud and live
in deep water; a few only are littoral species.
FAMILY ~SPATANGOIDÆ~
GENUS =Moira=
^M. atropos.^ Size about one inch by one and a half inches, and one
inch thick; color yellowish-white, with brown spines. Found from
North Carolina to Florida, from the shore to deep water.
[Illustration: PLATE LVIII. Clypeaster ravenellii. Mellita
testudinata. Encope michelini. Test of Metalia pectoralis. Lovenia
cordiformis.]
[pg227]
GENUS ^Lovenia^
^L. cordiformis.^ About one inch by one and a half inches thick;
reddish in color; resembles a little porcupine. Found on the
southern California coast. (Plate LVIII.)
GENUS ^Schizaster^
^S. fragilis.^ One and a half by two inches in size, and one inch
thick; color brownish. Lives in deep water off the eastern coast.
GENUS =Metalia=
^M. pectoralis.^ A very large heart-urchin, found on the southern
coast of Florida and in the West Indies in shallow water. It is,
perhaps, the largest species found, being six to eight inches long
and proportionately wide and thick. The shell is thin, more or less
elliptical, and densely clothed with long reddish-gray spines.
(Plate LVIII.)
GENUS ^Brissopsis^
^B. lyrifera.^ A beautiful deep-water species, found off the
coasts of Florida and the Gulf of Mexico. It has a red body with
pale-yellowish spines. In size it is about two by two and a half
inches, and is thickest on the posterior end. It is thickly clothed
with long curved spines, some of which form two long tufts in the
back. [pg228]
TABLE SHOWING THE CLASSIFICATION OF THE HOLOTHUROIDEA DESCRIBED IN
THIS CHAPTER
Class =HOLOTHUROIDEA=
Order =ELASIPODA= (/Deep-sea forms; tube-feet in zones near
together/)
Order =PEDATA= (/Well-developed tube-feet and false ambulacra/)
Genera Species
^Thyone^ ^T. briareus^
^Pentacta^ ^P. frondosa^
^Lophothuria^ ^L. fabricii^
Order =APODA= (/Without radial canals, tube-feet, or respiratory
trees/)
^Synapta^ ^S. tenuis^
^S. roseola^
^S. rotifera^
^Caudina^ ^C. arenata^
[pg229]
CLASS =HOLOTHUROIDEA=
SEA-CUCUMBERS
The holothurians, or sea-cucumbers, although in appearance quite
unlike starfishes and sea-urchins, have the characteristic ambulacral
zones and other features of the group. In form they are cylindrical,
and, when the tentacles and tube-feet are retracted, resemble fat
worms; when fully expanded they are somewhat like sea-anemones, the
tentacles forming a rosette-like top. The walls of the body are tough
and muscular, with small calcareous deposits or spicules of various
shapes in the skin. The mouth is at one end, the excretory opening
at the other, and along the body are double rows of tube-feet. Often
instead of tube-feet, or together with them, are conical processes
without suckers. The ambulacra, when arranged in regular zones, are
used for locomotion only in the lines running from the madreporic
plate. In some species three of the zones are near together, and form
a kind of sole on which the animal creeps; again the tube-feet are
wholly suppressed, as in /Synapta/. Besides progressing by means of
these suckers, the holothurians move, as do worms, by the extension
and contraction of the body. The inner surface of the tough membrane
inclosing the body is lined with powerful longitudinal and transverse
muscles, by means of which the creature contracts and lengthens its
body and changes its form in a wonderful manner. Around the mouth
are tentacles, which are often much branched and are used as organs
of touch and smell, and sometimes have an ear-sac at the base. From
the mouth the food-canal, making one long coil, extends to a chamber
[pg231] (/cloaca/) at the other pole. The cloaca gives off a pair
of much-branched respiratory trees, which are constantly supplied
with water by the contractions of the cloaca. At the base of one of
the respiratory trees are singular structures known as /Cuvierian
organs/. They are numerous, viscid, glandular tubes, which the animal
can throw out, and which will adhere closely to almost anything. The
holothurian has a water-vascular system, the madreporic plate being
near the mouth, but not opening to the outside, and a nervous system
which starts from a ring which lies around the mouth. The egg-sacs
are branched tubes, often highly colored, which open to the outside,
close to the wreath of tentacles surrounding the mouth.
[Illustration: Internal organs of a /Holothurian/, as seen when
the body-wall is divided along the middle of the dorsal surface:
/b.w./, body-wall; /circ. mus./, circular layer of muscle; /cl./,
cloaca; /cl. op./, cloacal opening with five teeth; /cuv. org./,
Cuvierian organs; /gen. ap./, genital aperture; /gen. du./, genital
duct; /gen. gl./, genital gland; /int./, intestine; /inter. oss./,
interambulacral ossicles; /int. ves./, intestinal vessels; /long.
mus./, longitudinal band of muscle; /mad. can./, madreporic canals;
/mes./, mesentery; /pol. ves./, Polian vesicles; /rad. amb./, radial
ambulacral vessel; /ri. bl. ves./, ring blood-vessel; /resp./,
respiratory trees; /ring-ves./, ring-vessel of the ambulacral system;
/stom./, stomach.]
The larvæ, when free-swimming, are called /Auricula/. In the
deep-water species, /Cucumaria crocea/ and /Psolus ephippiger/, the
eggs, when discharged, and the young are carried on the back of the
mother. In /Cucumaria lævigata/ there is a brood-pouch, while in
/Synapta viviparia/ the young develop in the body-cavity.
The holothurians have the singular power of ejecting the whole of
their internal organs and of growing them again in case they escape
the enemy they have endeavored to elude by this strange method. They
also turn themselves inside out, as it were, as if from /nausea/,
when confined in water too stale for their uses. Often the viscera
are ejected through holes in the sides of the body broken by violent
muscular contractions.
Holothurians are generally distributed through all seas, but are
congregated in greatest numbers in Eastern seas. Their habitat
extends from shallow to very deep water. They are found in
tide-pools, on rocks, and in sand or mud. Like worms, they live on
organic particles contained in mud and sand, which they take into the
gullet and pass through the alimentary canal.
ORDER =PEDATA=
GENUS ^Thyone^
^T. briareus.^ This is a large purple holothurian, found in shallow
water from Texas to Cape Cod. It is four to five inches long and
one inch or more thick, purple in color, and thickly covered over
its whole surface with prominent papillæ. [pg232]
GENUS ^Pentacta^
[Illustration: /Pentacta frondosa/, the sea-cucumber.]
^P. frondosa.^ This animal is commonly called the sea-cucumber,
and the popular name somewhat expresses its form, but it has the
power of changing its shape in a most surprising manner. Sometimes
it will be nearly globular, again long and thin, or it may be
constricted like an hourglass. When at rest the body is ovate and
somewhat pentagonal. On the angles are double lines of suckers, and
in the interambulacral zones are a few scattered false ambulacra.
The surface is nearly smooth, very dark purple on one side, and
inclined to whitish on the other. Ten much-branched tentacles
surround the mouth. The animal, when grown and expanded, measures
fifteen to eighteen inches in length. This species is found
throughout the whole length of both the east and the west coasts.
It is very plentiful on the Maine coast in tide-pools and on the
rocks at low-water mark. The genus ranges over the greater part of
the globe. The tough muscular body is said to be edible, tasting
somewhat like lobster, or trepang (/Holothuria edulis/), which is
found on coral reefs in Eastern seas and is much valued as food
by the Chinese. The internal organs of /P. frondosa/ are highly
colored, making its anatomy easy to trace. The muscular system is
plainly defined.
GENUS ^Lophothuria^
[Illustration: /Lophothuria fabricii/, showing under surface with
three rows of ambulacra.]
^L. fabricii^ (Verrill), ^Psolus fabricii^ (Düben), ^Cuvieria
squamata^ (D. and K.: Agassiz). The body in this species is covered
with rounded overlapping scales and numerous granulations, and
when it is retracted is about two and a half to three inches long
and about one inch thick. [pg233] Rows of tube-feet lie near
together, on a flat under surface, and form a kind of sole on which
the animal creeps. The oral end of the body is a little raised
and bears ten tentacles; these tentacles are profusely and finely
branched, and when expanded are about as long as the body. The
aboral end is obtuse and a little raised. Around the oral and anal
openings the scales are grouped, forming circles in those regions.
This holothurian is bright red in color, and when expanded is a
beautiful object, perhaps the most attractive in appearance of any
in the class. When retracted it has the aspect of an ascidian, and
for a time was supposed to belong to that group. It is found on the
New England coast on the under side of large shelving rocks.
ORDER =APODA=
GENUS ^Synapta^
^S. tenuis.^ This curious animal is long and slender, and so
transparent that its internal organs are clearly visible. Around
the mouth are a circular tube and a wreath of twelve branching
tentacles. There are no ambulacra. Little spots scattered
irregularly over the surface show, when highly magnified, small
warts, each one of which has a calcareous projection shaped like a
little anchor. By means of these anchors and by the contractions
of its body the animal moves through the mud or sand in which it
lives, near low-water mark. The sand is collected into rings at the
oral end and pushed downward until the whole animal is inclosed in
a sand-tube. When empty /Synapta/ is white and transparent, and
the digestive canal may be seen wound in a spiral throughout its
length; but when gorged with food, sand, pebbles, and shells can
be distinctly seen filling the food-canal, and the body then has a
dark-gray color. /Synapta/ grows to a length of eighteen inches or
more, but is constantly breaking pieces off its posterior end by
muscular contractions. When kept in confinement it soon commences
to constrict its body at various points, and after a few hours
there is nothing left but a mass of fragments. It is viviparous,
that is, it carries its young in the body-cavity; the eggs are
hatched, and the young approach maturity before they are expelled.
This species ranges from Cape Cod to North Carolina, and can be
found in the upper part of its burrows when the tide is out.
^S. roseola.^ This species occurs in the same localities as /S.
tenuis/, and differs from it mainly in color, which is pale red,
due to minute red spots scattered through the skin.
^S. rotifera.^ A species found in Florida. It is light purplish
in color, and has eight or ten branches on each of the twelve
tentacles. In this species the spicules of lime in the skin are
shaped like wheels instead of anchors.
GENUS ^Caudina^
^C. arenata.^ About four inches long and tapers to the ends; the
posterior end sometimes narrowed to a long, slender, tail-like
extremity; tentacles around the mouth resemble cloves. It lives in
sand and may be found on the New England coast, washed ashore after
a storm. [pg234]
Class =CRINOIDEA=
Genera ^Pentacrinus^ ^Comatula^
CLASS =CRINOIDEA=
FEATHER-STARS AND SEA-LILIES
[Illustration: The feather-star (/Antedon/), illustrating the
/Comatula/ form of crinoid.]
The crinoids are inhabitants of deep water, where they grow in great
numbers, forming beds of sea-lilies. Their general form, which
suggests the lily, and their feather-like manner of branching, give
them the two common names of sea-lilies and sea-feathers. They have
a long, jointed stalk, one end of which is attached, while the other
bears the disk of the animal. From the disk emanate five arms, which
divide near the base, making [pg235] ten arms in all. The arms
have short branches along the sides. Ambulacral grooves follow the
center of all the arms and branches. The mouth is in the center of
the upper side, which in this case is the ventral surface. The genus
^Pentacrinus^ remains permanently attached, but ^Comatula^, at a
certain stage of development, separates from the stalk and swims
freely about by means of its arms. It can attach itself temporarily
by tubular processes, which are developed on the dorsal surface at
the point where the stem was attached. The ossicles, or plates which
cover the dorsal surface, are free, making the crinoid an animal of
innumerable joints.
[Illustration: /Pentacrinus asteria./]
The crinoids are particularly interesting from the fact that they
have existed from early geologic times, and their history is written
in stone. In the early ages they were the only class of echinoderms,
and their evolution into other forms can be traced through successive
geologic periods. They existed in such vast numbers that the fossil
forms are plentiful and are familiar to every student of geology, and
are known as stone-lilies and encrinites. To-day they are decadent,
there now remaining only twelve of the two hundred genera which
existed formerly. A fine bed of crinoids is found off Cuba, on the
slope of the coast where the water rapidly deepens from one hundred
to two hundred fathoms. [pg236]
Although the crinoids are deep-water forms, and are never found on
the beach, they are given here because they follow in the system of
classification and illustrate another curious class of echinoderms.
The brief description given may add interest to the fossil forms to
be seen in museums.
VI
ARTHROPODA
TABLE SHOWING THE CLASSIFICATION OF THE ARTHROPODS DESCRIBED IN THIS
CHAPTER
Phylum =ARTHROPODA=
Class =CRUSTACEA=
Subclass =Entomostraca= (/Crustacea of small, often of almost
microscopic minuteness, and of comparatively simple
organization; appendages have little differentiation/)
Order =PHYLLOPODA= (/Appendages resemble leaves; mostly
fresh-water species/)
Suborder ~EUPHYLLOPODA~ (/Phyllopoda of considerable
size, bearing ten to sixty pairs of leaf-like
swimming-feet/)
Suborder ~CLADOCERA~ (/Small phyllopoda; body laterally
compressed; carapace like a bivalve shell; four to five
pairs of swimming-feet; chief organs of locomotion are
the biramous antennæ; abdomen devoid of appendages. They
abound in fresh water, are very prolific, and afford a
large amount of food to fresh-water fishes/)
Genera Species
^Daphnia^
^Leptodora^
^Moina^
^Polyphemus^
Order =OSTRACODA= (/Resemble minute bivalve shells; swim by
antennæ; body unsegmented; appendages seven pairs only/)
^Cypris^ (fresh-water)
^Cypridina^ (marine)